xwm: Don't leak pending.input region
xwm: Don't leak pending.input region

It's not really a leak, since the region is always a rectangle, but let's
play by the rules.

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