null safety

lib/pages/delivery/delivery_info.dart

@@ -60,9 +60,8 @@ class _DeliveryInfoState extends State<DeliveryInfo> {
   @override
   void initState() {
     super.initState();
-    if(widget.box != null)
-    _box = widget.box!;
-    _selectedCartonType = _box.cartonType;
+    if (widget.box != null) _box = widget.box!;
+    _selectedCartonType = _box.cartonType ?? '';
 
     //for shipment weight
     volumetricRatio = Provider.of<ShipmentRateModel>(context, listen: false)
@@ -81,7 +80,7 @@ class _DeliveryInfoState extends State<DeliveryInfo> {
     _heightController.text = _box.height.toString();
     _lengthController.text = _box.length.toString();
     _cargoTypes = _box.cargoTypes;
-    _deliveryAddress = _box.deliveryAddress;
+    _deliveryAddress = _box.deliveryAddress!;
     isMixBox = _box.cartonType == carton_mix_box;
     isFromShipments = _box.cartonType == carton_from_shipments;
     isFromPackages = _box.cartonType == carton_from_packages;
@@ -97,7 +96,7 @@ class _DeliveryInfoState extends State<DeliveryInfo> {
     if (_box.cartonType == carton_from_packages && _box.userID == null) return;
     PackageModel packageModel =
         Provider.of<PackageModel>(context, listen: false);
-    List<Package> packages = await packageModel.getPackages(_box.userID, [
+    List<Package> packages = await packageModel.getPackages(_box.userID!, [
       package_processed_status,
       package_packed_status,
       package_shipped_status,
@@ -136,8 +135,9 @@ class _DeliveryInfoState extends State<DeliveryInfo> {
     final cartonTypeBox = LocalRadioButtons(
         readOnly: true,
         values: cartonModel.cartonTypesInfo,
-        selectedValue:
-            _box.isShipmentCarton ? carton_from_shipments : _box.cartonType);
+        selectedValue: _box.isShipmentCarton ?? false
+            ? carton_from_shipments
+            : _box.cartonType);
     final shipmentBox = DisplayText(
       text: _box.fcsShipmentNumber,
       labelTextKey: "box.fcs_shipment_num",
@@ -174,11 +174,11 @@ class _DeliveryInfoState extends State<DeliveryInfo> {
         children: <Widget>[
           Expanded(
               child: new Text(
-            _selectedShipmentBox.shipmentNumber,
+            _selectedShipmentBox.shipmentNumber ?? "",
             style: textStyle,
           )),
           new Text(
-            _selectedShipmentBox.desc,
+            _selectedShipmentBox.desc ?? "",
             style: textStyle,
           ),
         ],

lib/pages/delivery/model/delivery_model.dart

@@ -42,7 +42,7 @@ class DeliveryModel extends BaseModel {
     if (listener != null) listener.cancel();
     _cartons = [];
     try {
-      listener = Firestore.instance
+      listener = FirebaseFirestore.instance
           .collection("$path")
           .where("status", isEqualTo: carton_shipped_status)
           .where("carton_type", whereIn: [