Hi, it's not so much that your news sitemap is empty as it appear empty to human eyes. This is because the associated stylesheet on /wp-content/plugins/xml-sitemap-feed/includes/xsl/sitemap-news.xsl.php (which is needed to make the XML file render human readable in a browser) causes an internal server error.
The PHP file that renders the stylesheet does not involve any complicated PHP so I'd be very curious to learn what that error is exactly.
Do you have access to your server (or hosting account) error log files? If so, could you trigger the error by opening the stylesheet URL directly in your browser and then opening the log files to see the latest entry(s)... You can send them to me via the contact form on http://status301.net/contact-en/
I'd be very grateful and will be looking for a solution ASAP :)