code: public function generate()
  	{
  		if (TL_MODE == 'BE')
  		{
  			$objTemplate = new BackendTemplate('be_wildcard');
  			$objTemplate->wildcard = '### ' . Utf8::strtoupper($GLOBALS['TL_LANG']['FMD']['calendar'][0]) . ' ###';
  			$objTemplate->title = $this->headline;
  			$objTemplate->id = $this->id;
  			$objTemplate->link = $this->name;
  			$objTemplate->href = 'contao/main.php?do=themes&amp;table=tl_module&amp;act=edit&amp;id=' . $this->id;
  
  			return $objTemplate->parse();
  		}
  
  		$this->cal_calendar = $this->sortOutProtected(StringUtil::deserialize($this->cal_calendar, true));
  
  		// Return if there are no calendars
  		if (empty($this->cal_calendar) || !\is_array($this->cal_calendar))
  		{
  			return '';
  		}
  
  		$this->strUrl = preg_replace('/\?.*$/', '', Environment::get('request'));
  		$this->strLink = $this->strUrl;
  
  		if (($objTarget = $this->objModel->getRelated('jumpTo')) instanceof PageModel)
  		{
  			/** @var PageModel $objTarget */
  			$this->strLink = $objTarget->getFrontendUrl();
  		}
  
  		return parent::generate();
  	}
docs: Do not show the module if no calendar has been selected
  
  @return string