Fix memory leak when Language header is defined more than once
Fix memory leak when Language header is defined more than once

Discovered by OSS-Fuzz.
Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=229.

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