Crash in music.c in the set_stem_dir

[Microsvuln]

There is a crash in set_stem_dir function in music.c file when parsing a malformed input .

Output :

poc5:27:37: error: Bad character '2'
AddressSanitizer:DEADLYSIGNAL
=================================================================
==22266==ERROR: AddressSanitizer: SEGV on unknown address 0x00000000003b (pc 0x00000056d80c bp 0x7fffabba7af0 sp 0x7fffabba6440 T0)
==22266==The signal is caused by a READ memory access.
==22266==Hint: address points to the zero page.
    #0 0x56d80c in set_stem_dir /home/arash/abcm2ps/music.c:2920:21
    #1 0x56d80c in output_music /home/arash/abcm2ps/music.c:5088:3
    #2 0x6b7a79 in generate /home/arash/abcm2ps/parse.c:1042:2
    #3 0x645f70 in gen_ly /home/arash/abcm2ps/parse.c:1063:2
    #4 0x645f70 in do_tune /home/arash/abcm2ps/parse.c:3643:2
    #5 0x349d7d in abc_parse /home/arash/abcm2ps/abcparse.c:179:4
    #6 0x542af3 in txt_add_eos /home/arash/abcm2ps/front.c:379:2
    #7 0x542af3 in frontend /home/arash/abcm2ps/front.c:891:4
    #8 0x33549c in treat_file /home/arash/abcm2ps/abcm2ps.c:240:2
    #9 0x339393 in main /home/arash/abcm2ps/abcm2ps.c:1041:3
    #10 0x7f2110bf6bf6 in __libc_start_main /build/glibc-S9d2JN/glibc-2.27/csu/../csu/libc-start.c:310
    #11 0x2868d9 in _start (/home/arash/abcm2ps/abcm2ps.laf.asan+0x2868d9)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /home/arash/abcm2ps/music.c:2920:21 in set_stem_dir
==22266==ABORTING

To reproduce :

./abcm2ps poc5
poc5.zip