anchor.diff:          _selectedIsolate.value =
               _isolateStates.isEmpty ? null : _isolateStates.keys.first;
         }
  +      _isolateRunnableCompleters.remove(event.isolate.id);
       }
     }
   
  
positive.code: 
    Future<void> _handleIsolateEvent(Event event) async {
      _sendToMessageBus(event);
  
      if (event.kind == EventKind.kIsolateStart &&
          !event.isolate.isSystemIsolate) {
        await _registerIsolate(event.isolate);
        _isolateCreatedController.add(event.isolate);
  
negative.code:   ValueListenable<IsolateRef> get mainIsolate => _mainIsolate;
    final _mainIsolate = ValueNotifier<IsolateRef>(null);
  
    final _isolateRunnableCompleters = <String, Completer<void>>{};
  
    Future<void> init(List<IsolateRef> isolates) async {
      // Re-initialize isolates when VM developer mode is enabled/disabled to
      // display/hide system isolates.
  