Prevent infinite loop via engine.dispose()
Prevent infinite loop via engine.dispose()

It appears that the MainSoundTrack was getting added to the scene's list of soundtracks, and receiving an id > -1. This caused multiple problems. The worst symptom was an infinite loop after calling engine.dispose()!
RaananW/Babylon.js,RaananW/Babylon.js,NicolasBuecher/Babylon.js,jbousquie/Babylon.js,jbousquie/Babylon.js,RaananW/Babylon.js,BabylonJS/Babylon.js,BabylonJS/Babylon.js,jbousquie/Babylon.js,NicolasBuecher/Babylon.js,sebavan/Babylon.js,Kesshi/Babylon.js,sebavan/Babylon.js,sebavan/Babylon.js,Kesshi/Babylon.js,BabylonJS/Babylon.js,Kesshi/Babylon.js,NicolasBuecher/Babylon.js