x11: don't wait until window is destroyed

This can hang if the window was destroyed externally (or that's what I
suspect happens), and we somehow didn't receive the DestroyNotify event.
I'm not sure why we wouldn't receive this event (since it should just be
in the xlib event queue), but on the other hand there's no real need to
wait for window destruction.

This essentially reverts 97fc74e2.