process_karaoke_effects: place line at infinity except during \kf
process_karaoke_effects: place line at infinity except during \kf

Fixes \k and \ko in https://github.com/libass/libass/issues/357.

xbmc/libass,ShiftMediaProject/libass,libass/libass,ShiftMediaProject/libass,xbmc/libass,astiob/libass,Akemi/libass,MrSmile/libass,MrSmile/libass,Akemi/libass,astiob/libass,libass/libass,Akemi/libass