update main model

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