/**
  * defines the default image
  *
  * @param string $image path to the default image file, relative to the WP root
  */
 public function set_default_image($image = false)
 {
     if (!$image) {
         $this->default_image = Participants_Db::$plugin_options['default_image'];
     } else {
         $this->default_image = $image;
     }
     $default_image = trailingslashit(PDb_Path::base_url()) . ltrim($this->default_image, '/');
     //    error_log(__METHOD__.' setting: '.$this->default_image.' full: '.$default_image);
     if (!empty($this->default_image) and @getimagesize($default_image)) {
         $this->default_image = $default_image;
     } else {
         $this->default_image = false;
     }
 }