xwayland: Don't crash when we get configure notify for destroyed frame windows
xwayland: Don't crash when we get configure notify for destroyed frame windows

We can get a destroy notify for the frame window after we've removed it
from the hash table.  This turns into a NULL pointer deref when we look up
the window and try to use it for debugging printout.

Fixes the failing xwayland test case.

eyolfson/weston,Tarnyko/weston-xdg_surface_present,giucam/weston,giucam/weston,sir-murray/weston,kwm81/weston,krezovic/weston,mchalupa/weston,mchalupa/weston,udoprog/weston,xorgy/weston,Fantu/compositor-spice,xorgy/weston,krezovic/weston,Gnurou/weston,Fantu/compositor-spice,sir-murray/weston,eyolfson/weston,Gnurou/weston,jonnylamb/weston,udoprog/weston,Tarnyko/weston-xdg_surface_present,jonnylamb/weston,kwm81/weston,Fantu/compositor-spice