message: Don't skip modified shaders when tex viewer is just in another tab
  * We only want to skip these events if the texture viewer has actually
  been closed and destroyed.
diff: @@ -1132,7 +1132,7 @@ public void OnLogfileLoaded()
  void CustomShaderModified(object sender, FileSystemEventArgs e)
  {
  - if (!Visible || IsDisposed) return;
  + if (IsDisposed) return;
  Thread.Sleep(5);
  BeginInvoke((MethodInvoker)delegate
  