vorbisfile free of uninitialized memory if seek fails
In vorbisfile.c, it is possible for ov_raw_seek to free some uninitialized memory (and therefore crash) if seek fails. I attach a patch to fix this bug.
This was originally discovered by an SFML user in this bug, and I investigated it a bit more: https://github.com/SFML/SFML/issues/1241