fix(core): sort channels with disposed state last instead of crashing

packages/stream_chat_flutter_core/CHANGELOG.md

@@ -9,6 +9,7 @@
 🐞 Fixed
 
 - Fixed `StreamChannel`'s default error state exposing raw error details; it now shows a safe error state (icon, message, and a Try Again button wired to `retry()`) that adapts to the failure type.
+- Fixed `StreamChannelListController` crashing with a null-check error when its local sort ran over a channel disposed mid-query (e.g. a client disconnect/logout racing an in-flight `loadMore`); such channels are now sorted last instead.
 
 ## 10.2.0
 

packages/stream_chat_flutter_core/lib/src/stream_channel_list_controller.dart

@@ -155,8 +155,17 @@ class StreamChannelListController extends PagedValueNotifier<int, Channel> {
         orElse: () => newValue,
         (success) => success.copyWith(
           items: success.items.sortedByCompare(
-            (it) => it.state!.channelState,
-            channelSort.compare,
+            // A channel loses its state when it is disposed — e.g. a client
+            // disconnect/logout or a channel-removal event racing an
+            // in-flight query — so sort stateless channels last instead of
+            // null-asserting on them.
+            (it) => it.state?.channelState,
+            (a, b) => switch ((a, b)) {
+              (null, null) => 0,
+              (null, _) => 1,
+              (_, null) => -1,
+              (final a?, final b?) => channelSort.compare(a, b),
+            },
           ),
         ),
       ),

packages/stream_chat_flutter_core/test/stream_channel_list_controller_test.dart

@@ -275,6 +275,33 @@ void main() {
     expect((captured.single as PaginationParams).offset, equals(nextPageKey));
   });
 
+  test('local sort places channels with disposed state last instead of crashing', () {
+    ChannelState channelStateFor({required DateTime createdAt}) => ChannelState(
+      channel: ChannelModel(cid: 'messaging:${createdAt.millisecondsSinceEpoch}', createdAt: createdAt),
+    );
+
+    final older = MockChannel();
+    when(() => older.state.channelState).thenReturn(channelStateFor(createdAt: DateTime(2026, 1, 1)));
+
+    final newer = MockChannel();
+    when(() => newer.state.channelState).thenReturn(channelStateFor(createdAt: DateTime(2026, 6, 1)));
+
+    // A channel disposed while a query is in flight (client disconnect or
+    // logout, a channel-removal event) has its state nulled out.
+    final disposed = NonInitializedMockChannel();
+
+    final controller = StreamChannelListController(
+      client: client,
+      channelStateSort: defaultChannelListSort,
+    );
+
+    expect(
+      () => controller.value = PagedValue<int, Channel>(items: [disposed, older, newer]),
+      returnsNormally,
+    );
+    expect(controller.value.asSuccess.items, equals([newer, older, disposed]));
+  });
+
   // The controller's only responsibility for events is routing them to the
   // matching handler method. The handler's behavior for each event is covered
   // in stream_channel_list_event_handler_test.dart, so here we inject a mock