diff --git a/lib/domain/entities/setting.dart b/lib/domain/entities/setting.dart
index c0aefe1..dd85745 100644
--- a/lib/domain/entities/setting.dart
+++ b/lib/domain/entities/setting.dart
@@ -9,7 +9,7 @@ List<Day> dayLists = [
 ];
 
 class Setting {
-  final int? supportBuildNum;
+  final int supportBuildNum;
   // contact page
   String? usaAddress;
   String? mmAddress;
@@ -27,7 +27,7 @@ class Setting {
   List<String> shipmentTypes;
 
   Setting(
-      {this.supportBuildNum,
+      {this.supportBuildNum = 1,
       this.usaAddress,
       this.mmAddress,
       this.usaContactNumber,
diff --git a/lib/domain/entities/user.dart b/lib/domain/entities/user.dart
index ae917fe..0ad4100 100644
--- a/lib/domain/entities/user.dart
+++ b/lib/domain/entities/user.dart
@@ -16,8 +16,8 @@ class User {
   String? fcsID;
   DateTime? lastMessageTime;
   String? lastMessage;
-  int? userUnseenCount;
-  int? fcsUnseenCount;
+  int userUnseenCount;
+  int fcsUnseenCount;
   String? preferCurrency;
 
   String get initial =>
@@ -42,12 +42,12 @@ class User {
   }
 
   String get getUserUnseenCount => userUnseenCount != null
-      ? userUnseenCount! > 100
+      ? userUnseenCount > 100
           ? "99+"
           : userUnseenCount.toString()
       : "0";
   String get getFcsUnseenCount => fcsUnseenCount != null
-      ? fcsUnseenCount! > 100
+      ? fcsUnseenCount > 100
           ? "99+"
           : fcsUnseenCount.toString()
       : "0";
@@ -72,8 +72,8 @@ class User {
       this.privileges = const [],
       this.lastMessage,
       this.lastMessageTime,
-      this.userUnseenCount,
-      this.fcsUnseenCount,
+      this.userUnseenCount = 0,
+      this.fcsUnseenCount = 0,
       this.preferCurrency});
 
   factory User.fromJson(Map<String, dynamic> json) {
diff --git a/lib/pages/buying_instruction/buying_online.dart b/lib/pages/buying_instruction/buying_online.dart
index 44d3436..fbd8b53 100644
--- a/lib/pages/buying_instruction/buying_online.dart
+++ b/lib/pages/buying_instruction/buying_online.dart
@@ -1,6 +1,5 @@
 import 'package:fcs/helpers/theme.dart';
 import 'package:fcs/pages/main/model/main_model.dart';
-import 'package:fcs/pages/main/util.dart';
 import 'package:fcs/pages/widgets/display_text.dart';
 import 'package:fcs/pages/widgets/fcs_id_icon.dart';
 import 'package:fcs/pages/widgets/local_text.dart';
@@ -28,22 +27,22 @@ class _BuyingOnlinePagetate extends State<BuyingOnlinePage>
     MainModel mainModel = Provider.of<MainModel>(context);
 
     final phoneNumberBox = DisplayText(
-      text: mainModel.user.phone,
+      text: mainModel.user?.phone,
       labelTextKey: "contact.phone",
       iconData: Icons.location_on,
     );
     final nameBox = Center(
         child: Text(
-      mainModel.user.name,
+      mainModel.user?.name ?? "",
       style: TextStyle(fontSize: 18, color: primaryColor),
     ));
     final fcsIdBox = DisplayText(
-      text: mainModel.user.fcsID,
+      text: mainModel.user?.fcsID,
       labelTextKey: "customer.fcs.id",
       icon: FcsIDIcon(),
     );
     final shippingAddressBox = DisplayText(
-      text: mainModel.setting.usaAddress,
+      text: mainModel.setting?.usaAddress,
       labelTextKey: "profile.usa.shipping.address",
       iconData: Icons.location_on,
     );
diff --git a/lib/pages/carton/model/carton_model.dart b/lib/pages/carton/model/carton_model.dart
index 24d3aeb..e8694dc 100644
--- a/lib/pages/carton/model/carton_model.dart
+++ b/lib/pages/carton/model/carton_model.dart
@@ -3,9 +3,7 @@ import 'dart:async';
 import 'package:cloud_firestore/cloud_firestore.dart';
 import 'package:fcs/data/services/services.dart';
 import 'package:fcs/domain/constants.dart';
-import 'package:fcs/domain/entities/cargo_type.dart';
 import 'package:fcs/domain/entities/carton.dart';
-import 'package:fcs/domain/vo/message.dart';
 import 'package:fcs/domain/vo/shipment_status.dart';
 import 'package:fcs/helpers/paginator.dart';
 import 'package:fcs/pages/main/model/base_model.dart';
@@ -14,13 +12,14 @@ import 'package:logging/logging.dart';
 
 class CartonModel extends BaseModel {
   List<Carton> _boxes = [];
-  PaginatorListener cartonsByFilter;
+  PaginatorListener? cartonsByFilter;
 
   final log = Logger('CartonModel');
-  List<Carton> get boxes =>
-      _selectedIndex == 1 ? _boxes : List<Carton>.from(_delivered.values);
+  List<Carton> get boxes => _selectedIndex == 1
+      ? _boxes
+      : List<Carton>.from(_delivered?.values ?? []);
 
-  Paginator _delivered;
+  Paginator? _delivered;
   int _selectedIndex = 1;
   int _selectedIndexFilter = 1;
   bool isLoading = false;
@@ -87,17 +86,17 @@ class CartonModel extends BaseModel {
     notifyListeners();
   }
 
-  get selectedIndex => _selectedIndex;
-  get selectedIndexFilter => _selectedIndexFilter;
+  int get selectedIndex => _selectedIndex;
+  int get selectedIndexFilter => _selectedIndexFilter;
 
   initData() async {
     _selectedIndex = 1;
     _selectedIndexFilter = 1;
     _loadBoxes();
 
-    if (_delivered != null) _delivered.close();
+    if (_delivered != null) _delivered!.close();
     _delivered = _getDelivered();
-    _delivered.load();
+    _delivered!.load();
   }
 
   @override
diff --git a/lib/pages/chat/model/message_model.dart b/lib/pages/chat/model/message_model.dart
index 447a325..e075fd2 100644
--- a/lib/pages/chat/model/message_model.dart
+++ b/lib/pages/chat/model/message_model.dart
@@ -26,7 +26,8 @@ class MessageModel extends BaseModel {
   StreamSubscription<QuerySnapshot> listener;
 
   static const int rowPerLoad = 20;
-  void initQuery(String userID) {
+  void initQuery(String? userID) {
+    if(userID == null)return;
     this.messages = [];
     this.userID = userID;
     this.prevSnap = null;
diff --git a/lib/pages/customer/model/customer_model.dart b/lib/pages/customer/model/customer_model.dart
index 8dda2f0..ea9525c 100644
--- a/lib/pages/customer/model/customer_model.dart
+++ b/lib/pages/customer/model/customer_model.dart
@@ -90,7 +90,7 @@ class CustomerModel extends BaseModel {
     }
   }
 
-  Future<User> getUser(String id) async {
+  Future<User> getUser(String? id) async {
     String path = "/$user_collection";
     var snap = await Firestore.instance.collection(path).document(id).get();
     return User.fromMap(snap.data, snap.documentID);
diff --git a/lib/pages/main/home_page.dart b/lib/pages/main/home_page.dart
index d1dcf98..abd2f86 100644
--- a/lib/pages/main/home_page.dart
+++ b/lib/pages/main/home_page.dart
@@ -84,7 +84,7 @@ class _HomePageState extends State<HomePage> {
   }
 
   _loadStaffMode(bool isCustomer) async {
-    bool staffMode = await SharedPref.getStaffMode();
+    bool? staffMode = await SharedPref.getStaffMode();
     setState(() {
       if (isCustomer) {
         isFcs[0] = false;
@@ -117,12 +117,12 @@ class _HomePageState extends State<HomePage> {
     if (mainModel.isLogin()) {
       timer.cancel();
       bool isCustomer = mainModel.isCustomer();
-      String receiverID = isCustomer ? mainModel.user.id : notiUserID;
-      String receiverName = isCustomer ? mainModel.user.name : notiUserName;
+      String? receiverID = isCustomer ? mainModel.user?.id : notiUserID;
+      String? receiverName = isCustomer ? mainModel.user?.name : notiUserName;
       MessageModel messageModel =
           Provider.of<MessageModel>(context, listen: false);
       messageModel.initQuery(receiverID);
-      User user = mainModel.user;
+      User user = mainModel.user!;
       if (!isCustomer) {
         CustomerModel customerModel =
             Provider.of<CustomerModel>(context, listen: false);
@@ -133,15 +133,15 @@ class _HomePageState extends State<HomePage> {
           MaterialPageRoute(
               builder: (context) => MessageDetail(
                     messageModel: messageModel,
-                    receiverID: receiverID,
-                    receiverName: receiverName,
+                    receiverID: receiverID ?? "",
+                    receiverName: receiverName ?? "",
                   ))).then((value) {
         if (user.userUnseenCount > 0) {
-          messageModel.seenMessages(user.id, true);
+          messageModel.seenMessages(user.id ?? "", true);
         }
       });
       if (user.userUnseenCount > 0) {
-        messageModel.seenMessages(user.id, true);
+        messageModel.seenMessages(user.id ?? "", true);
       }
     }
   }
@@ -204,7 +204,7 @@ class _HomePageState extends State<HomePage> {
 
   @override
   Widget build(BuildContext context) {
-    User user = Provider.of<MainModel>(context).user;
+    User? user = Provider.of<MainModel>(context).user;
 
     if (user == null) {
       Future.microtask(
@@ -280,11 +280,11 @@ class _HomePageState extends State<HomePage> {
       ))
           .then((value) {
         if (user.userUnseenCount > 0) {
-          messageModel.seenMessages(user.id, true);
+          messageModel.seenMessages(user.id ?? "", true);
         }
       });
       if (user.userUnseenCount > 0) {
-        messageModel.seenMessages(user.id, true);
+        messageModel.seenMessages(user.id ?? "", true);
       }
     });
     final notiBtn = badgeCounter(notiBtnOrg, user.userUnseenCount);
diff --git a/lib/pages/main/initial_language_selection.dart b/lib/pages/main/initial_language_selection.dart
index 0253db3..7ce4cfe 100644
--- a/lib/pages/main/initial_language_selection.dart
+++ b/lib/pages/main/initial_language_selection.dart
@@ -26,9 +26,9 @@ class _InitialLanguageSelectionPageState
     languagesList[1]: languageCodesList[1],
   };
 
-   String selectedLanguage = 'en';
+  String selectedLanguage = 'en';
   late int selectedIndex;
-   bool _isLoading = false;
+  bool _isLoading = false;
 
   @override
   void initState() {
@@ -101,8 +101,8 @@ class _InitialLanguageSelectionPageState
                                   ? BoxDecoration()
                                   : BoxDecoration(
                                       border: Border(
-                                        bottom:
-                                            BorderSide(color: Colors.grey.shade300),
+                                        bottom: BorderSide(
+                                            color: Colors.grey.shade300),
                                       ),
                                     ),
                               child: ListTile(
@@ -177,7 +177,7 @@ class _InitialLanguageSelectionPageState
     setState(() {
       selectedIndex = index;
       selectedLanguage = lang;
-      Translation().onLocaleChanged!(Locale(languagesMap[lang]));
+      Translation().onLocaleChanged(Locale(languagesMap[lang]));
       Provider.of<LanguageModel>(context, listen: false)
           .saveLanguage(selectedLanguage);
     });
diff --git a/lib/pages/main/model/base_model.dart b/lib/pages/main/model/base_model.dart
index a0b82d0..a5cbc4f 100644
--- a/lib/pages/main/model/base_model.dart
+++ b/lib/pages/main/model/base_model.dart
@@ -6,9 +6,9 @@ import 'package:fcs/helpers/api_helper.dart';
 import 'main_model.dart';
 
 abstract class BaseModel extends ChangeNotifier {
-  User user;
-  Setting setting;
-  MainModel mainModel;
+  User? user;
+  Setting? setting;
+  MainModel? mainModel;
 
   void initUser(User user) async {
     this.user = user;
@@ -16,7 +16,7 @@ abstract class BaseModel extends ChangeNotifier {
 
   void privilegeChanged() {}
 
-  void initSetting(Setting setting) async {
+  void initSetting(Setting? setting) async {
     this.setting = setting;
   }
 
@@ -32,8 +32,8 @@ abstract class BaseModel extends ChangeNotifier {
     String path,
     method, {
     dynamic payload,
-    String token,
-    String url,
+    required String token,
+    String? url,
   }) async {
     return await requestAPI(path, method,
         payload: payload, token: token, url: url);
diff --git a/lib/pages/main/model/language_model.dart b/lib/pages/main/model/language_model.dart
index b6bd04c..5be6d4e 100644
--- a/lib/pages/main/model/language_model.dart
+++ b/lib/pages/main/model/language_model.dart
@@ -5,7 +5,7 @@ import 'package:flutter/painting.dart';
 import 'base_model.dart';
 
 class LanguageModel extends BaseModel {
-  String language;
+  late String language;
   bool get isEng => this.language == "English";
   List<bool> get currentState => isEng ? [true, false] : [false, true];
 
diff --git a/lib/pages/main/model/main_model.dart b/lib/pages/main/model/main_model.dart
index 5f2180e..67a963b 100644
--- a/lib/pages/main/model/main_model.dart
+++ b/lib/pages/main/model/main_model.dart
@@ -15,16 +15,16 @@ class MainModel extends ChangeNotifier {
   final log = Logger('MainModel');
   List<BaseModel> models = [];
 
-  String messagingToken;
-  User user;
-  PackageInfo packageInfo;
+  String? messagingToken;
+  User? user;
+  PackageInfo? packageInfo;
 
   set setMessaginToken(token) {
     this.messagingToken = token;
     uploadMsgToken();
   }
 
-  Setting setting;
+  Setting? setting;
 
   bool isLoaded = false;
   bool isOnline = false;
@@ -42,23 +42,23 @@ class MainModel extends ChangeNotifier {
   }
 
   bool faqEditable() {
-    return this.user != null && this.user.hasSupport();
+    return this.user != null && this.user!.hasSupport();
   }
 
   bool rateEditable() {
-    return this.user != null && this.user.hasSupport();
+    return this.user != null && this.user!.hasSupport();
   }
 
   bool paymentMethodsEditable() {
-    return this.user != null && this.user.hasSupport();
+    return this.user != null && this.user!.hasSupport();
   }
 
   bool termEditable() {
-    return this.user != null && this.user.hasSupport();
+    return this.user != null && this.user!.hasSupport();
   }
 
   bool contactEditable() {
-    return this.user != null && this.user.hasSupport();
+    return this.user != null && this.user!.hasSupport();
   }
 
   bool isLogin() {
@@ -66,32 +66,31 @@ class MainModel extends ChangeNotifier {
   }
 
   bool isCustomer() {
-    return user != null && user.isCustomer();
+    return user != null && user!.isCustomer();
   }
 
   bool isSysAdmin() {
-    return this.user != null && this.user.hasSysAdmin();
+    return this.user != null && this.user!.hasSysAdmin();
   }
 
   bool isAdmin() {
-    return this.user != null && this.user.hasAdmin();
+    return this.user != null && this.user!.hasAdmin();
   }
 
   // userListener should never be closed
-  StreamSubscription<User> userListener;
+  StreamSubscription<User?>? userListener;
   _init() async {
     await _listenSetting();
-    this.isFirstLaunch = await SharedPref.isFirstLaunch();
-    this.isFirstLaunch = this.isFirstLaunch ?? true;
+    this.isFirstLaunch = await SharedPref.isFirstLaunch() ?? true;
     this.packageInfo = await PackageInfo.fromPlatform();
 
-    if (userListener != null) userListener.cancel();
+    if (userListener != null) userListener!.cancel();
     userListener =
         Services.instance.authService.getUserStream().listen((_user) {
       if (_user != null) {
         models.forEach((m) => m.initUser(_user));
         // call diffPrivileges if privilege changed or first time login
-        if (this.user == null || _user.diffPrivileges(this.user)) {
+        if (this.user == null || _user.diffPrivileges(this.user!)) {
           models.forEach((m) => m.privilegeChanged());
         }
         if (this.user == null) {
@@ -124,7 +123,7 @@ class MainModel extends ChangeNotifier {
 
   bool isSupport() {
     if (packageInfo == null || setting == null) return false;
-    return int.parse(packageInfo.buildNumber) >= setting.supportBuildNum;
+    return int.parse(packageInfo!.buildNumber) >= setting!.supportBuildNum;
   }
 
   Future<AuthResult> sendSms(String phoneNumber) {
@@ -137,14 +136,14 @@ class MainModel extends ChangeNotifier {
     return authResult;
   }
 
-  Future<void> uploadMsgToken() {
+  Future<void>? uploadMsgToken() {
     if (messagingToken == null || user == null) return null;
-    return Services.instance.userService.uploadMsgToken(messagingToken);
+    return Services.instance.userService.uploadMsgToken(messagingToken!);
   }
 
-  Future<void> removeMsgToken() {
+  Future<void>? removeMsgToken() {
     if (messagingToken == null || user == null) return null;
-    return Services.instance.userService.removeMsgToken(messagingToken);
+    return Services.instance.userService.removeMsgToken(messagingToken!);
   }
 
   Future<void> signout() async {