Use navigator instead of overlay as TickerProvider for ModalBottomSheet (#93499)

packages/flutter/lib/src/material/bottom_sheet.dart

@@ -508,7 +508,7 @@ class _ModalBottomSheetRoute<T> extends PopupRoute<T> {
       _animationController = transitionAnimationController;
       willDisposeAnimationController = false;
     } else {
-      _animationController = BottomSheet.createAnimationController(navigator!.overlay!);
+      _animationController = BottomSheet.createAnimationController(navigator!);
     }
     return _animationController!;
   }

packages/flutter/test/material/bottom_sheet_test.dart

@@ -51,6 +51,43 @@ void main() {
     FlutterError.onError = handler;
   });
 
+  testWidgets('Disposing app while bottom sheet is disappearing does not crash', (WidgetTester tester) async {
+    late BuildContext savedContext;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Builder(
+          builder: (BuildContext context) {
+            savedContext = context;
+            return Container();
+          },
+        ),
+      ),
+    );
+
+    await tester.pump();
+    expect(find.text('BottomSheet'), findsNothing);
+
+    // Bring up bottom sheet.
+    bool showBottomSheetThenCalled = false;
+    showModalBottomSheet<void>(
+      context: savedContext,
+      builder: (BuildContext context) => const Text('BottomSheet'),
+    ).then<void>((void value) {
+      showBottomSheetThenCalled = true;
+    });
+    await tester.pumpAndSettle();
+    expect(find.text('BottomSheet'), findsOneWidget);
+    expect(showBottomSheetThenCalled, isFalse);
+
+    // Start closing animation of Bottom sheet.
+    tester.state<NavigatorState>(find.byType(Navigator)).pop();
+    await tester.pump();
+
+    // Dispose app by replacing it with a container. This shouldn't crash.
+    await tester.pumpWidget(Container());
+  });
+
   testWidgets('Tapping on a modal BottomSheet should not dismiss it', (WidgetTester tester) async {
     late BuildContext savedContext;