docs: protected void ensureEventSource(UUID eventSource, Event event) {
  		if (event.getSource() == null) {
  			if (eventSource != null) {
  				event.setSource(new Address(getSpaceID(), eventSource));
  			} else {
  				throw new AssertionError("Every event must have a source"); //$NON-NLS-1$
  			}
  		}
  	}