cleanup code

lib/pages/invoice/editor/invoice_editor.dart

@@ -1,3 +1,5 @@
+// ignore_for_file: unnecessary_null_comparison
+
 import 'package:fcs/domain/entities/cargo_type.dart';
 import 'package:fcs/domain/entities/carton.dart';
 import 'package:fcs/domain/entities/custom_duty.dart';
@@ -81,7 +83,8 @@ class _InvoiceEditorState extends State<InvoiceEditor> {
       await _loadCartons();
       await _loadShipments();
       await _loadDiscount();
-    } catch (e) {} finally {
+    } catch (e) {
+    } finally {
       setState(() {
         _isLoading = false;
       });
@@ -118,7 +121,7 @@ class _InvoiceEditorState extends State<InvoiceEditor> {
     DiscountModel discountModel =
         Provider.of<DiscountModel>(context, listen: false);
     discounts = (await discountModel.getDiscount(widget.customer!.id!))!;
-    if (discounts != null && discounts.length > 0) {
+    if (discounts.isNotEmpty) {
       setState(() {
         _invoice!.discount = discounts.first;
       });
@@ -257,7 +260,7 @@ class _InvoiceEditorState extends State<InvoiceEditor> {
                       InvoiceHandlingFeeList(shipments: _invoice!.shipments)));
           _addShipment(shipment);
         } else if (p.id == 3) {
-          Discount discount =
+          Discount? discount =
               await Navigator.of(context).push(CupertinoPageRoute(
                   builder: (context) => InvoiceDiscountList(
                         discounts: discounts,
@@ -412,7 +415,7 @@ class _InvoiceEditorState extends State<InvoiceEditor> {
       showMsgDialog(context, "Error", "Expected at least one cargo type");
       return;
     }
-    if ((amount ) <= 0) {
+    if ((amount) <= 0) {
       showMsgDialog(context, "Error", "Expected positive amount");
       return;
     }