Error makefulltextfeed.php

I have an error when fetch url:http://phuot.net/threads/ban-la-ai-hay-noi-cho-moi-nguoi-biet-di-nao.243/

This is pattern:
body: //div[@class=‘messageContent’]//img[contains(@src,’.jpg’)]
next_page_link: substring-after(substring-after(//div[@class=‘PageNav’]/nav/a[contains(text(), ‘Tiếp >’)]/@href, ‘/’), ‘/’)

Warning: DOMDocument::importNode(): Couldn’t fetch JSLikeHTMLElement in /var/www/rssleech/makefulltextfeed.php on line 852

Catchable fatal error: Argument 1 passed to DOMNode::appendChild() must be an instance of DOMNode, null given in /var/www/rssleech/makefulltextfeed.php on line 853