update

lib/pages/discount/discount_list.dart

@@ -16,7 +16,7 @@ import 'discount_editor.dart';
 class DiscountList extends StatefulWidget {
   final bool selectionMode;
 
-  const DiscountList({Key key, this.selectionMode = false}) : super(key: key);
+  const DiscountList({Key? key, this.selectionMode = false}) : super(key: key);
   @override
   _DiscountListState createState() => _DiscountListState();
 }
@@ -62,7 +62,7 @@ class _DiscountListState extends State<DiscountList> {
         appBar: AppBar(
           centerTitle: true,
           title: Text(
-            AppTranslations.of(context).text("discount.title"),
+            AppTranslations.of(context)!.text("discount.title"),
           ),
           leading: new IconButton(
             icon: new Icon(CupertinoIcons.back),