/**
  * Set currency as default
  *
  * @param void
  * @return null
  */
 function set_as_default()
 {
     if ($this->active_currency->isNew()) {
         $this->httpError(HTTP_ERR_NOT_FOUND);
     }
     // if
     if ($this->request->isSubmitted()) {
         $update = Currencies::setDefault($this->active_currency);
         if ($update && !is_error($update)) {
             $this->httpOk();
         } else {
             $this->serveData($update);
         }
         // if
     } else {
         $this->httpError(HTTP_ERR_BAD_REQUEST);
     }
     // if
 }