[Fuzzer] SIGSEGV found in mon.c

[Soviet5lo]

#0  0x00005555556838e2 in make_corpse (mtmp=0x555555c729d0) at src/mon.c:506
#1  0x000055555568cae0 in xkilled (mtmp=mtmp@entry=0x555555c729d0, dest=<optimized out>, dest@entry=1) at src/mon.c:2475
#2  0x000055555568ceda in killed (mtmp=mtmp@entry=0x555555c729d0) at src/mon.c:2347
#3  0x0000555555765388 in hmon_hitmon (mon=0x555555c729d0, obj=<optimized out>, thrown=<optimized out>) at src/uhitm.c:1904
#4  0x0000555555762835 in hmon (mon=mon@entry=0x555555c729d0, obj=<optimized out>, thrown=thrown@entry=0) at src/uhitm.c:748
#5  0x000055555576d643 in known_hitum (mon=mon@entry=0x555555c729d0, mattack=1, mhit=mhit@entry=0x7fffffffcc88, uattk=uattk@entry=0x55555587cad0 <upermonst+16>) at src/uhitm.c:574
#6  0x0000555555771c50 in hmonas (tmp=<optimized out>, mon=0x555555c729d0) at src/uhitm.c:3214
#7  attack (mtmp=mtmp@entry=0x555555c729d0) at src/uhitm.c:512
#8  0x000055555562a931 in domove () at src/hack.c:1550
#9  0x00005555555bc636 in rhack (cmd=<optimized out>, cmd@entry=0x0) at src/cmd.c:3782
#10 0x0000555555590ebc in moveloop () at src/allmain.c:654
#11 0x000055555558fbac in main (argc=<optimized out>, argv=<optimized out>) at sys/unix/unixmain.c:309

Program received signal SIGSEGV, Segmentation fault.
0x00005555556838e2 in make_corpse (mtmp=0x555555c729d0) at src/mon.c:506
506             obj->oinvis = mtmp->perminvis;