Fixes out of array read
Fixes: asan_heap-oob_fb5c50_19_018.rmvb
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 10e32618)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>