fix: Chat list flickering

lib/pages/chat_list.dart

@@ -166,9 +166,10 @@ class ChatListController extends State<ChatList> {
   void initState() {
     _initReceiveSharingIntent();
     WidgetsBinding.instance.addPostFrameCallback(
-      (_) => waitForFirstSync().then((_) => checkBootstrap()),
+      (_) => waitForFirstSync.then((_) => checkBootstrap()),
     );
     scrollController.addListener(_onScroll);
+    waitForFirstSync = _waitForFirstSync();
     super.initState();
   }
 
@@ -384,7 +385,9 @@ class ChatListController extends State<ChatList> {
     setState(() => selectedRoomIds.clear());
   }
 
-  Future<void> waitForFirstSync() async {
+  Future<void> waitForFirstSync;
+
+  Future<void> _waitForFirstSync() async {
     final client = Matrix.of(context).client;
     await client.roomsLoading;
     await client.accountDataLoading;

lib/pages/views/chat_list_view.dart

@@ -430,7 +430,7 @@ class _ChatListViewBody extends StatelessWidget {
           .rateLimit(const Duration(seconds: 1)),
       builder: (context, snapshot) {
         return FutureBuilder<void>(
-          future: controller.waitForFirstSync(),
+          future: controller.waitForFirstSync,
           builder: (BuildContext context, snapshot) {
             if (snapshot.connectionState == ConnectionState.done) {
               final rooms = Matrix.of(context)