/**
  * Update the event with the information returned by the callback.
  *
  * @param GetParentHeaderEvent $event The event being emitted.
  *
  * @param array                $value The additional information.
  *
  * @return void
  */
 public function update($event, $value)
 {
     if ($value === null) {
         return;
     }
     $event->setAdditional($value);
     $event->stopPropagation();
 }