Pro Sites php warning on many pages

I'm close to launching our multi-site hosting service but I keep seeing this php warning on various pages:

Warning: array_diff(): Argument #1 is not an array in /home/spsite/public_html/wp-content/plugins/pro-sites/pro-sites-files/modules/premium-plugins-manager.php on line 322

Here's a screenshot of the registration /pro-site page:

Do I have something configured incorrectly? If not any thoughts on how to fix it?

I have debug in my wp-config file turned off.


Bob Patterson