/**
  * Renders a view
  *
  * @param string $viewName view name
  * @return string result of the rendering
  */
 protected function render($viewName)
 {
     try {
         $output = parent::render($viewName);
     } catch (InvalidParamException $e) {
         $output = parent::render('_form');
     }
     return $output;
 }