Crashing when deleting events with the engine running

[vustav]

In another issue I have started I was reminded that for a while I haven't actually deleted events when the engine is running because of crashes. Instead I've used a class that I send them to after removing them from the sequencer to be deleted when the sequencer stops. Today I tried deleting them right away and the crashes are still there. These are the steps:

for(events){
event.enable(false);
event.removeFromSequencer();
event.delete();
}
instrument.getAudioChannel().getProcessingChain().reset();
instrument.getAudioChannel().getProcessingChain().delete();
instrument.delete();

This is the stack from firebase:

[igorski]

Continued in #179