Fix a ModalbottomSheet bug (#99970)

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

@@ -2357,6 +2357,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin, Resto
     late _StandardBottomSheet bottomSheet;
 
     bool removedEntry = false;
+    bool doingDispose = false;
     void _removeCurrentBottomSheet() {
       removedEntry = true;
       if (_currentBottomSheet == null) {
@@ -2380,11 +2381,19 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin, Resto
     final LocalHistoryEntry? entry = isPersistent
       ? null
       : LocalHistoryEntry(onRemove: () {
-          if (!removedEntry && _currentBottomSheet?._widget == bottomSheet) {
+          if (!removedEntry && _currentBottomSheet?._widget == bottomSheet && !doingDispose) {
             _removeCurrentBottomSheet();
           }
         });
 
+    void _removeEntryIfNeeded() {
+      if (!isPersistent && !removedEntry) {
+        assert(entry != null);
+        entry!.remove();
+        removedEntry = true;
+      }
+    }
+
     bottomSheet = _StandardBottomSheet(
       key: bottomSheetKey,
       animationController: animationController,
@@ -2394,11 +2403,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin, Resto
           return;
         }
         assert(_currentBottomSheet!._widget == bottomSheet);
-        if (!isPersistent && !removedEntry) {
-          assert(entry != null);
-          entry!.remove();
-          removedEntry = true;
-        }
+        _removeEntryIfNeeded();
       },
       onDismissed: () {
         if (_dismissedBottomSheets.contains(bottomSheet)) {
@@ -2408,6 +2413,8 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin, Resto
         }
       },
       onDispose: () {
+        doingDispose = true;
+        _removeEntryIfNeeded();
         if (shouldDisposeAnimationController) {
           animationController.dispose();
         }

packages/flutter/test/material/bottom_sheet_test.dart

@@ -1149,6 +1149,50 @@ void main() {
     expect(tester.takeException(), isNull);
   });
 
+  // Regression test for https://github.com/flutter/flutter/issues/99627
+  testWidgets('The old route entry should be removed when a new sheet popup', (WidgetTester tester) async {
+    final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey();
+    PersistentBottomSheetController<void>? sheetController;
+
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        key: scaffoldKey,
+        body: const Center(child: Text('body')),
+      ),
+    ));
+
+    final ModalRoute<dynamic> route = ModalRoute.of(scaffoldKey.currentContext!)!;
+    expect(route.canPop, false);
+
+    scaffoldKey.currentState!.showBottomSheet<void>((_) {
+      return Builder(
+        builder: (BuildContext context) {
+          return Container(height: 200.0);
+        },
+      );
+    });
+
+    await tester.pump();
+    expect(find.byType(BottomSheet), findsOneWidget);
+    expect(route.canPop, true);
+
+    // Trigger the second sheet will remove the first sheet from tree.
+    sheetController = scaffoldKey.currentState!.showBottomSheet<void>((_) {
+      return Builder(
+        builder: (BuildContext context) {
+          return Container(height: 200.0);
+        },
+      );
+    });
+    await tester.pump();
+    expect(find.byType(BottomSheet), findsOneWidget);
+    expect(route.canPop, true);
+
+    sheetController.close();
+
+    expect(route.canPop, false);
+  });
+
   // Regression test for https://github.com/flutter/flutter/issues/87708
   testWidgets('The framework does not dispose of the transitionAnimationController provided by user.', (WidgetTester tester) async {
     const Key tapTarget = Key('tap-target');