http://bugs.winehq.org/show_bug.cgi?id=31702
--- Comment #31 from Henri Verbeet hverbeet@gmail.com 2012-09-24 05:52:03 CDT --- (In reply to comment #30)
This is because !data->clip_hwnd .
Is that always the case? It would get set to NULL by ungrab_clipping_window(), but after a successful call to clip_fullscreen_window() (grab_clipping_window()) it's supposed to be non-NULL.