fontselect: cleanup lazy font index evaluation
fontselect: cleanup lazy font index evaluation

Fixes a possible NULL pointer dereference, reported by Coverity.

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