FRED Asserts with scripting and async calls

[MjnMixael]

I was trying to use async to essentially force a script to init after a downstream script where the file hierarchy kinda made naming for priority tricky and ran into this. Basically if you use on async call with the onFrameExecutor, it expects a game state which of course is invalid in FRED. It triggers the assert in gamesequence.cpp on line 437 because FRED is not in a game state.

I don't know a whole lot about the async code so I didn't try anything really but I'm wondering if we could either create a GS_STATE_FRED = -1 enumeration for the game states or perhaps if Fred_running at line 437, return some kind of preset value since FRED can't really have other states. I'm not sure if there's other places the onFrameExecutor might break down in FRED, though.