message: Fix potential crash on macOS
diff: @@ -195,7 +195,7 @@ void MainWindow::installTouchBar()
  void MainWindow::updateTouchBar(int ahead, int behind)
  {
  NSView *view = reinterpret_cast<NSView *>(winId());
  - if ([view.window.delegate isKindOfClass:[TouchBarProvider class]]) {
  + if (view && [view.window.delegate isKindOfClass:[TouchBarProvider class]]) {
  TouchBarProvider *provider = (TouchBarProvider *) view.window.delegate;
  [provider updateRemoteAhead:ahead behind:behind];
  }
  