check null safety

lib/domain/entities/shipment.dart

@@ -4,35 +4,35 @@ import 'package:fcs/domain/entities/carton.dart';
 import 'package:fcs/domain/vo/delivery_address.dart';
 
 class Shipment {
-  String id;
-  String shipmentNumber;
-  String shipmentType;
-  DeliveryAddress pickupAddress;
-  DateTime pickupDate;
-  String pickupTimeStart;
-  String pickupTimeEnd;
+  String? id;
+  String? shipmentNumber;
+  String? shipmentType;
+  DeliveryAddress? pickupAddress;
+  DateTime? pickupDate;
+  String? pickupTimeStart;
+  String? pickupTimeEnd;
 
-  String userName;
-  String userID;
-  String phoneNumber;
-  int numberOfPackage;
-  int weight;
-  double handlingFee;
-  double paidHandlingFee;
-  String address;
-  String status;
+  String? userName;
+  String? userID;
+  String? phoneNumber;
+  int numberOfPackage = 0;
+  int weight = 0;
+  double handlingFee = 0;
+  double paidHandlingFee = 0;
+  String? address;
+  String? status;
   bool isCourier;
   int radioIndex;
   List<Carton> boxes;
 
-  String pickupUserID;
-  String pickupUserName;
-  String pickupUserPhoneNumber;
+  String? pickupUserID;
+  String? pickupUserName;
+  String? pickupUserPhoneNumber;
 
-  String fcsShipmentID;
-  String fcsShipmentNumber;
-  String shipmentLabelUrl;
-  bool isSelected;
+  String? fcsShipmentID;
+  String? fcsShipmentNumber;
+  String? shipmentLabelUrl;
+  bool isSelected = false;
 
   Shipment(
       {this.id,
@@ -43,28 +43,28 @@ class Shipment {
       this.phoneNumber,
       this.pickupTimeStart,
       this.pickupTimeEnd,
-      this.numberOfPackage,
-      this.weight,
-      this.handlingFee,
-      this.paidHandlingFee,
+      this.numberOfPackage = 0,
+      this.weight = 0,
+      this.handlingFee = 0,
+      this.paidHandlingFee = 0,
       this.address,
       this.status,
       this.pickupDate,
       this.isCourier = false,
       this.radioIndex = 1,
-      this.pickupAddress,
+      required this.pickupAddress,
       this.pickupUserID,
       this.pickupUserName,
       this.pickupUserPhoneNumber,
       this.fcsShipmentID,
       this.fcsShipmentNumber,
       this.shipmentLabelUrl,
-      this.boxes});
+      this.boxes = const []});
 
-  int get last => DateTime.now().difference(pickupDate).inDays;
+  // int get last => DateTime.now().difference(pickupDate).inDays;
 
-  double get totalWeight => boxes?.fold(0, (p, e) => p + e.actualWeight);
-  int get totalCount => boxes?.length;
+  double get totalWeight => boxes.fold(0, (p, e) => p + e.actualWeight);
+  int get totalCount => boxes.length;
 
   bool get isPending => status == shipment_pending_status;
   bool get isAssigned => status == shipment_assigned_status;
@@ -100,15 +100,15 @@ class Shipment {
   }
 
   Map<String, dynamic> toMap() {
-    List _boxes = boxes?.map((l) => l.toMap())?.toList() ?? [];
+    List _boxes = boxes.map((l) => l.toMap()).toList();
 
     return {
       "id": id,
       'user_id': userID,
       'cartons': _boxes,
       'shipment_type': shipmentType,
-      'pickup_address': pickupAddress.toMap(),
-      "pickup_date": pickupDate?.toUtc()?.toIso8601String(),
+      'pickup_address': pickupAddress?.toMap(),
+      "pickup_date": pickupDate?.toUtc().toIso8601String(),
       'pickup_time_start': pickupTimeStart,
       'pickup_time_end': pickupTimeEnd,
       'pickup_user_id': pickupUserID,