null safety

lib/pages/widgets/status_tree.dart

@@ -4,7 +4,7 @@ import 'package:fcs/domain/vo/shipment_status.dart';
 import 'package:fcs/helpers/theme.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_icons/flutter_icons.dart';
+import 'package:flutter_vector_icons/flutter_vector_icons.dart';
 import 'package:intl/intl.dart';
 import 'package:timeline_list/timeline.dart';
 import 'package:timeline_list/timeline_model.dart';
@@ -12,10 +12,10 @@ import 'package:timeline_list/timeline_model.dart';
 var dateFormatter = new DateFormat('dd MMM yyyy');
 
 class StatusTree extends StatelessWidget {
-  final List<ShipmentStatus> shipmentHistory;
-  final String currentStatus;
+  final List<ShipmentStatus>? shipmentHistory;
+  final String? currentStatus;
 
-  const StatusTree({Key key, this.shipmentHistory, this.currentStatus})
+  const StatusTree({Key? key, this.shipmentHistory, this.currentStatus})
       : super(key: key);
   @override
   Widget build(BuildContext context) {
@@ -39,7 +39,7 @@ class StatusTree extends StatelessWidget {
     if (shipmentHistory == null || currentStatus == null) return [];
     bool isPacked = currentStatus != package_received_status &&
         currentStatus != package_processed_status;
-    return shipmentHistory
+    return shipmentHistory!
         .map((e) => TimelineModel(
             Padding(
               padding: const EdgeInsets.all(18.0),
@@ -48,17 +48,17 @@ class StatusTree extends StatelessWidget {
                 children: <Widget>[
                   Text(e.status,
                       style: TextStyle(
-                          color: e.done ? primaryColor : Colors.grey,
+                          color: e.done! ? primaryColor : Colors.grey,
                           fontSize: 16,
                           fontWeight: FontWeight.bold)),
-                  e.done || isPacked
+                  e.done! || isPacked
                       ? Text(dateFormatter.format(e.date))
                       : Container(),
-                  e.staffName == null ? Container() : Text(e.staffName)
+                  e.staffName == null ? Container() : Text(e.staffName!)
                 ],
               ),
             ),
-            iconBackground: e.done ? primaryColor : Colors.grey,
+            iconBackground: e.done! ? primaryColor : Colors.grey,
             icon: Icon(
               e.status == "shipped"
                   ? Ionicons.ios_airplane