[iA1]

It is php error. Just remove e from preg_replace.

Updated code will be like this:

// Start IMG to URL BBCode Converter
if ($this->contains_bbcode_img_tags($message)) 
        {
        $message = preg_replace('#\[img\]\s*(https?://([^<>*"]+|[a-z0-9/\\._\- !]+))\[/img\]#iU', "\$this->handle_bbcode_url(str_replace('\\\"', '\"', '\\1'), '')", $message);
        }
// End IMG to URL BBCode Converter