as requested, [] - free

This should fix Bug 262540. It is not the same patch as in the Bugtracker. I listened to Martins advise and made it so that filtering all windows no longer closes the view.

This is my first submission so sorry if I did it the wrong way. I'm open to any advise I can get

Tested against git-master. Filtering out all windows keeps the view open, as soon as the last window is closed the view closes as well.