public function preSubmitData(FormEvent $event)
    {
        $form = $event->getForm();
        $data = $event->getData();

        if (null === $data || '' === $data) {
            $data = array();
        }

        foreach ($form as $name => $child) {
            if (!isset($data[$name])) {
                $form->remove($name);
            }
        }
    }