directwrite: fix broken return value check
directwrite: fix broken return value check

Akemi/libass,stps/libass,xbmc/libass,ShiftMediaProject/libass,stps/libass,MrSmile/libass,libass/libass,astiob/libass,MrSmile/libass,xbmc/libass,mwgoldsmith/libass,grigorig/libass,Akemi/libass,grigorig/libass,stps/libass,mwgoldsmith/libass,mwgoldsmith/libass,Akemi/libass,astiob/libass,libass/libass,ShiftMediaProject/libass