Fixes: 260813283176b57b3c9974fe284eebc3_signal_sigsegv_7ffff713351a_991_xtrem_e2_m64q15_a32sxx.3gp with memlimit of 262144

Found-by: Samuel Groß, Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>