![Jonas Dreßler](/assets/img/avatar_default.png)
The thumbnails actor `this._thumbnails` has already been destroyed when calling `_destroyThumbnails()` from the `destroy` signal handler because it is a child actor of the AppSwitcherPopup. So stop destroying the thumbnails separately (fading them out inside a destroy handler wouldn't make sense anyway). https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/167