phase3: nullfix.py batch script — bang/late/param-nullable

Automated null-safety fixes driven by dart analyze (no corruption):
- unchecked_use_of_nullable_value: insert '!' on receiver (property/method/[]/op)
- not_initialized field/var: mark 'late'
- missing_default_value_for_parameter: nullable param
Errors: 2374(peak) -> 907

lib/widgets/desktop/shop_promote.dart

@@ -22,7 +22,7 @@ class ShopPromoteState extends State<ShopPromote> {
   double sideSpace = 0;
   double mainSpace = 1200;
 
-  Business _business;
+  late Business _business;
 
   @override
   Widget build(BuildContext context) {
@@ -90,7 +90,7 @@ class ShopPromoteState extends State<ShopPromote> {
       mainAxisAlignment: MainAxisAlignment.start,
       children: <Widget>[],
     );
-    for (var i = 0; i < _business.promoProducts.length; i++) {
+    for (var i = 0; i < _business.promoProducts!.length; i++) {
       promotRow.children.add(Container(
         padding: EdgeInsets.only(
           left: 10.0,
@@ -129,17 +129,17 @@ class ShopPromoteState extends State<ShopPromote> {
             GestureDetector(
               child: Container(
                 child: Util.showImage(
-                  _business.promoProducts[i].imagePath,
+                  _business.promoProducts![i].imagePath,
                   width: 120.0,
                 ),
               ),
               onTap: () {
-                _showProductDetail(_business.promoProducts[i]);
+                _showProductDetail(_business.promoProducts![i]);
               },
             ),
             Container(
               child: Text(
-                _business.promoProducts[i].name,
+                _business.promoProducts![i].name,
                 maxLines: 2,
                 overflow: TextOverflow.ellipsis,
                 style: TextStyle(fontSize: 14.0),
@@ -149,16 +149,16 @@ class ShopPromoteState extends State<ShopPromote> {
               mainAxisAlignment: MainAxisAlignment.spaceBetween,
               children: <Widget>[
                 ShowPrice(
-                  _business.promoProducts[i].price,
+                  _business.promoProducts![i].price,
                   currencySign: '\$',
                   fontWeight: FontWeight.bold,
                   smallFontSize: 15,
                   largeFontSize: 24,
-                  regularPrice: _business.promoProducts[i].regularPrice,
+                  regularPrice: _business.promoProducts![i].regularPrice,
                 ),
                 Container(
                   child: AddRemoveButton(
-                    product: _business.promoProducts[i],
+                    product: _business.promoProducts![i],
                     business: _business,
                     addOnly: true,
                   ),