shell: Don't remove grab listener if surface was destroyed
shell: Don't remove grab listener if surface was destroyed

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