Event listeners calls removeListener

Hey all

I'm not sure if this is more suitable to put into the GitHub (i.e. it's a bug) or there's a known workaround / correct pattern for this issue (hence forum).

Here's the rub:

I have 3 classes:
* Gui controller A
* Gui element B (owned by A)
* Interactive camera C (owned by B)

Right now both A and C are listening to ofEvents().keyPressed.
If the user presses delete, then:

1. A deletes B
2. This causes B to delete C
3. In the destructor of C it removes the liseners to ofEvents().keyPressed

But this then causes a crash, because in ofEvents.h we have:

inline void notify(const void* sender, T & param){
	if(ofEvent<T,Mutex>::enabled && !ofEvent<T,Mutex>::functions.empty()){
		std::vector<of::priv::Function<T>*> functions_copy; // (--1--)
		{
			std::unique_lock<Mutex> lck(ofEvent<T,Mutex>::mtx);
			std::transform(ofEvent<T,Mutex>::functions.begin(), ofEvent<T,Mutex>::functions.end(),
					std::back_inserter(functions_copy),
					[&](of::priv::Function<T>&f){return &f;});
		}
		for(auto & f: functions_copy){
			if(f->function(sender,param)){ //(--2--)
				throw ofEventAttendedException();
			}
		}
	}
}

notice (--1--), where it creates a copy of all the functions its going to call before calling them one by one.

So, what happens is that it notify caches a list of functions it wants to call, one of those calls removeListener (which makes functions_copy), then notify continues to call functions in the list functions_copy. And at (--2--) we get...Ker-ash!!!!

@arturo - this seems to be your party from the git history? Is there a workaround (other than leaving a flag to do the deletion next frame or something like that. but that would still happen on the update listener somehow so can't see how it solves the problem)