public function placeholder_image_fallback($html, $post_id, $post_thumbnail_id, $size, $attr)
    {
        if ($html === '' && Config::get('images.placeholder_dir') !== false) {
            $html = $this->image_service->get_placeholder_image($post_id, $post_thumbnail_id, $size, $attr);
        }

        return $html;
    }