editor: fix assert to take preedit string into account
editor: fix assert to take preedit string into account

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