Crash in MemToBlock when playing corrupted MKV

Valgrind and sample attached

Backtrace:

#0 0x00007ffff6b99058 in ?? () from /lib/libc.so.6 #1 (closed) 0x00007fffecc40dd4 in MemToBlock (p_mem=0x7fffd83f9bfa '\020' <repeats 200 times>..., i_mem=1038256, offset=0) at /usr/include/bits/string3.h:52 #2 (closed) 0x00007fffecc41fc2 in BlockDecode (p_demux=0x7fffe8013da8, block=0x7fffd80bf3f0, simpleblock=0x0, i_pts=0, i_duration=, f_mandatory=true) at ../../../../modules/demux/mkv/mkv.cpp:545 #3 (closed) 0x00007fffecc42261 in Demux (p_demux=0x7fffe8013da8) at ../../../../modules/demux/mkv/mkv.cpp:718 #4 0x00007ffff793da8e in demux_Demux (p_demux=0x7fffe8013da8) at ../../src/input/demux.h:44 #5 (closed) MainLoopDemux (i_start_mdate=96076599146, pb_demux_polled=, pb_changed=, p_input=0x12f3788) at ../../src/input/input.c:583 #6 (closed) MainLoop (p_input=0x12f3788, b_interactive=) at ../../src/input/input.c:754 #7 (closed) 0x00007ffff793e1f5 in Run (obj=0x12f3788) at ../../src/input/input.c:545 #8 (closed) 0x00007ffff7009df0 in start_thread () from /lib/libpthread.so.0 #9 (closed) 0x00007ffff6b4b39d in clone () from /lib/libc.so.6 #10 (closed) 0x0000000000000000 in ?? ()