code: public HandlerRegistration setLocationNotFoundHandler(LocationNotFoundHandler handler) {
  		if (handlerManager.getHandlerCount(LocationNotFoundHandler.TYPE) > 0) {
  			LocationNotFoundHandler previous = handlerManager.getHandler(LocationNotFoundHandler.TYPE, 0);
  			handlerManager.removeHandler(LocationNotFoundHandler.TYPE, previous);
  		}
  		return handlerManager.addHandler(LocationNotFoundHandler.TYPE, handler);
  	}
docs: Set the {@link LocationNotFoundHandler} handler.
  <p/>
  There can only be one handler, the default shows a Js warning message.
  
  @param handler "no location found" handler
  @return handler registration.