private function getTranslationDomain(FormInterface $form)
	{
		$translation = $form->getConfig()->getOption('translation_domain');
		if (empty($translation))
		{
			$parent = $form->getParent();

			if (empty($parent))
			    $translation = 'messages';

			while (empty($translation))
			{
				$translation = $parent->getConfig()->getOption('translation_domain');
				$parent      = $parent->getParent();
				if (! $parent instanceof FormInterface && empty($translation))
					$translation = 'messages';
			}
		}

		return $translation = $translation === 'messages' ? null : $translation;  // Allow the Symfony Default setting to be used by returning null.
	}