Fix races that occur when a window id is destroyed and recreated very quickly. This...

Fix races that occur when a window id is destroyed and recreated very quickly. This behaviour happens when restarting the window manager.

Don't use windows that are destroyed when restacking other windows or when handling events on a window id.  It is possible for the same window id to appear in the window list multiple times if it is destroyed then created before the destroy fade-out completes.