/**
  * Validates the object right after it was loaded/initialized.
  *
  * We ensure that the custom_data field is an array.
  *
  * @since  1.0.0
  */
 public function prepare_obj()
 {
     parent::prepare_obj();
     if (!is_array($this->custom_data)) {
         $this->custom_data = array();
     }
 }