WordPress Theme Unit Test Data Problems

Hello,

I installed WordPress' "Theme Unit Test Data" and I'm getting strange... errors. For example at this link:
http://them-demo.sirius-designs.com/about-2/

I get:
"Fatal error: Class 'WP_Screen' not found in /home/sirius11/public_html/them-demo/wp-content/themes/upfront/elements/upfront-this-post/lib/this_post.php on line 539"

And similar with pages from the Theme Unit Test Data generated content. I don't know what the issue is, but it 'seems' like its something coming from the upfront theme.

Does anyone else know how to fix this or has/have had similar problems?

Best,

Robert S.