Improve disposable interface for mainvm

Author: Jack251970

Flow.Launcher/ViewModel/MainViewModel.cs

@@ -1554,6 +1554,8 @@ protected virtual void Dispose(bool disposing)
                 if (disposing)
                 {
                     _updateSource?.Dispose();
+                    _resultsUpdateChannelWriter?.Complete();
+                    _resultsViewUpdateTask?.Dispose();
                     _disposed = true;
                 }
             }