ZDoom

https://github.com/ZDoom/gzdoom/pull/1852

This shouldn't be too hard to fix, but I may not be able to get to this immediately. I'll respond here again once I have a fix. Unless of course someone beats me to it.

version "4.9.0"

class Test : Actor
{
	States
	{
	Spawn:
		PLAY A -1 NoDelay A_ChangeModel("bogus");
		Stop;
	}
}

If I specify a invalid modeldef to use via A_ChangeModel, the engine will lock up/freeze and I have to kill gzdoom via Task Manager.
I would prefer if it printed an error message instead. Saying the modeldef specified doesn't exist or something.

Load this zscript example for yourself, summon Test, close the console and gzdoom should freeze:
[code]version "4.9.0"

class Test : Actor
{
States
{
Spawn:
PLAY A -1 NoDelay A_ChangeModel("bogus");
Stop;
}
}
[/code]