Fixes out of array access
Fixes: signal_sigsegv_324b135_3398_cov_246853371_short.flac
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit e5c01ccd)

Conflicts:

	libavcodec/flacdec.c