Don't halve nonempty line height even if wholly invisible
Don't halve nonempty line height even if wholly invisible

VSFilter compatibility: VSFilter does no special handling
of invisible control characters and sees the line as nonempty.

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