Oh another one of mine... I haven't looked at it in a while, and this one was never up to full bulletproof status... I'll prowl through the code and see what's up.
Based on what I'm looking at, it may not be "getting" an emitter, probably after it's removed from the faderList...
delete faderList[emitterid];
So it looks like it's trying to process a fader that's already removed. I'm not sure how to "fix" that as I'm not sure how it's currently being used. The faders are mainly used to transition from one volume level to another on move.
The emitter ID is used because it establishes a unique ID for each emitter and consequently the fader. Each emitter (currently) should only have one fader controlling a shift in volume.
...and testing my old copy, it seems to be working...
Getting some weird bugs regarding sounds not starting up again once they've been ended a first time unless you manually start them playing...
All in all, it's in a severely unfinished state, unfortunately - I'd have to revisit it to try and get it working and working reliably.