Unregisters a previously registered event handler from this node. One handler might have been registered for different event types, so the caller needs to specify the particular event type from which to unregister the handler.

Parameters:

<T>		the specific event class of the handler
eventType		the event type from which to unregister
eventHandler		the handler to unregister

Exceptions:

NullPointerException

if the event type or handler is null