check null safety

lib/pages/user_search/user_list_row.dart

@@ -3,23 +3,12 @@ import 'package:fcs/helpers/theme.dart';
 import 'package:fcs/pages/user_search/user_serach.dart';
 import 'package:flutter/material.dart';
 
-class UserListRow extends StatefulWidget {
-  final OnUserRowSelect onUserRowSelect;
+class UserListRow extends StatelessWidget {
+  final OnUserRowSelect? onUserRowSelect;
   final User user;
-  const UserListRow({this.user, this.onUserRowSelect});
+  const UserListRow({required this.user, this.onUserRowSelect});
 
-  @override
-  _UserListRowState createState() => _UserListRowState();
-}
-
-class _UserListRowState extends State<UserListRow> {
   final double dotSize = 15.0;
-  User user;
-  @override
-  void initState() {
-    super.initState();
-    this.user = widget.user;
-  }
 
   @override
   Widget build(BuildContext context) {
@@ -30,8 +19,7 @@ class _UserListRowState extends State<UserListRow> {
         color: Colors.white,
         child: InkWell(
           onTap: () {
-            if (widget.onUserRowSelect != null)
-              widget.onUserRowSelect(widget.user);
+            if (onUserRowSelect != null) onUserRowSelect!(user);
           },
           child: Row(
             children: <Widget>[
@@ -53,17 +41,17 @@ class _UserListRowState extends State<UserListRow> {
                           crossAxisAlignment: CrossAxisAlignment.start,
                           children: <Widget>[
                             new Text(
-                              user.name == null ? '' : user.name,
+                              user.name ?? "",
                               style: new TextStyle(
                                   fontSize: 15.0, color: Colors.black),
                             ),
                             new Text(
-                              user.fcsID == null ? "" : user.fcsID,
+                              user.fcsID ?? "",
                               style: new TextStyle(
                                   fontSize: 13.0, color: Colors.grey),
                             ),
                             new Text(
-                              user.phoneNumber == null ? "" : user.phoneNumber,
+                              user.phoneNumber ?? "",
                               style: new TextStyle(
                                   fontSize: 13.0, color: Colors.grey),
                             ),

lib/pages/user_search/user_serach.dart

@@ -8,8 +8,8 @@ import 'package:provider/provider.dart';
 typedef OnUserSelect(User suer);
 typedef OnUserRowSelect(User suer);
 
-Future<User> searchUser(BuildContext context,
-        {OnUserSelect onUserSelect, bool popPage = false}) async =>
+Future<User?> searchUser(BuildContext context,
+        {required OnUserSelect onUserSelect, bool popPage = false}) async =>
     await showSearch<User>(
       context: context,
       delegate:
@@ -20,7 +20,7 @@ class UserSearchDelegate extends SearchDelegate<User> {
   final OnUserSelect onUserSelect;
   final bool popPage;
 
-  UserSearchDelegate({this.onUserSelect, this.popPage});
+  UserSearchDelegate({required this.onUserSelect, required this.popPage});
 
   @override
   String get searchFieldLabel => 'Search by FCS ID or Name';
@@ -31,10 +31,10 @@ class UserSearchDelegate extends SearchDelegate<User> {
     return theme.copyWith(
       inputDecorationTheme: InputDecorationTheme(
           hintStyle: TextStyle(
-              color: theme.primaryTextTheme.caption.color, fontSize: 14)),
+              color: theme.primaryTextTheme.caption?.color, fontSize: 14)),
       textTheme: theme.textTheme.copyWith(
-          title: theme.textTheme.title.copyWith(
-              color: theme.primaryTextTheme.title.color, fontSize: 16)),
+          title: theme.textTheme.title?.copyWith(
+              color: theme.primaryTextTheme.title?.color, fontSize: 16)),
       primaryColor: primaryColor,
     );
   }
@@ -53,7 +53,7 @@ class UserSearchDelegate extends SearchDelegate<User> {
   Widget buildLeading(BuildContext context) {
     return IconButton(
       icon: Icon(Icons.arrow_back),
-      onPressed: () => close(context, null),
+      onPressed: () => close(context, new User()),
     );
   }
 
@@ -64,7 +64,7 @@ class UserSearchDelegate extends SearchDelegate<User> {
         future: packageModel.searchUser(query),
         builder: (context, AsyncSnapshot<List<User>> snapshot) {
           if (snapshot.hasData) {
-            if (snapshot.data.length == 0) {
+            if (snapshot.data == null || snapshot.data!.length == 0) {
               return Container(
                 child: Center(
                   child: Text(
@@ -77,7 +77,7 @@ class UserSearchDelegate extends SearchDelegate<User> {
             return Container(
               padding: EdgeInsets.only(top: 15),
               child: ListView(
-                children: snapshot.data
+                children: snapshot.data!
                     .map((u) => UserListRow(
                           user: u,
                           onUserRowSelect: (u) => _onUserRowSelect(context, u),