shaper: drop no-op symbol = 0 assignment
shaper: drop no-op symbol = 0 assignment

Currently, this assignment affects nothing, as every subsequent `symbol`
check is paired with a `skip` check. However, the next commit will move
this code to an earlier pipeline stage where we need the original `symbol`.

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