public function showFallbackWarning()
    {
        $request = $this->requestStack->getCurrentRequest();

        if ($request->query->has('act')) {
            return;
        }

        $messages = \System::importStatic('Messages');
        \Message::addRaw($messages->languageFallback());

        if ($this->hasInvalidTopLevels()) {
            \Message::addRaw('<p class="tl_error">'.$GLOBALS['TL_LANG']['ERR']['topLevelRegular'].'</p>');
        }
    }