This also Happens in Skulltag, So I'm sure it is a Zdoom Bug
How to Reproduce:
Create a autoexec.cfg file containing only the line
atexit "snd_musicvolume 0.5"
and a new .ini crashes Skulltag r3151-Recent Beta and ZDoom 2.5.0 every time.
Not sure if its Intended. I was asked to make this report, so Feel free to yell at me