shorter nullable list duplications (#30305)

examples/catalog/lib/animated_list.dart

@@ -119,7 +119,7 @@ class ListModel<E> {
     Iterable<E> initialItems,
   }) : assert(listKey != null),
        assert(removedItemBuilder != null),
-       _items = List<E>.from(initialItems ?? <E>[]);
+       _items = initialItems?.toList() ?? <E>[];
 
   final GlobalKey<AnimatedListState> listKey;
   final dynamic removedItemBuilder;

examples/flutter_gallery/lib/demo/shrine/expanding_bottom_sheet.dart

@@ -613,7 +613,7 @@ class _ListModel {
     Iterable<int> initialItems,
   }) : assert(listKey != null),
        assert(removedItemBuilder != null),
-       _items = List<int>.from(initialItems ?? <int>[]);
+       _items = initialItems?.toList() ?? <int>[];
 
   final GlobalKey<AnimatedListState> listKey;
   final dynamic removedItemBuilder;

packages/flutter_test/lib/src/matchers.dart

@@ -1813,7 +1813,7 @@ class _MatchesSemanticsData extends Matcher {
       final List<CustomSemanticsAction> providedCustomActions = data.customSemanticsActionIds.map((int id) {
         return CustomSemanticsAction.getAction(id);
       }).toList();
-      final List<CustomSemanticsAction> expectedCustomActions = List<CustomSemanticsAction>.from(customActions ?? const <int>[]);
+      final List<CustomSemanticsAction> expectedCustomActions = customActions?.toList() ?? <CustomSemanticsAction>[];
       if (hintOverrides?.onTapHint != null)
         expectedCustomActions.add(CustomSemanticsAction.overridingAction(hint: hintOverrides.onTapHint, action: SemanticsAction.tap));
       if (hintOverrides?.onLongPressHint != null)