Pro Sites Error

I have Multisite activated and Pro sites installed on my site
Whenever I go to the checkout page:
it shows the following Pro Sites error:

Warning: array_keys() expects parameter 1 to be array, null given in /home4/icon/public_html/wp-content/plugins/pro-sites/pro-sites-files/lib/ProSites/View/Front/Checkout.php on line 108

I would appreciate your help,
Thank You very much!