private function getWidgetClass(PropertyInterface $property)
    {
        if (!isset($GLOBALS['TL_FFL'][$property->getWidgetType()])) {
            return null;
        }

        $className = $GLOBALS['TL_FFL'][$property->getWidgetType()];
        if (!class_exists($className)) {
            return null;
        }

        return $className;
    }