ass_font: fix broken loop condition
ass_font: fix broken loop condition

As pointed out in #198. This is certainly just a typo.

Fixes #198.

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