code: public function showFallbackWarning()
  	{
  		if (Contao\Input::get('act') != '')
  		{
  			return;
  		}
  
  		$messages = new Contao\Messages();
  		Contao\Message::addRaw($messages->languageFallback());
  	}
docs: Show a warning if there is no language fallback page