Pro Sites gives error in multisite signup page


I have Pro Sites installed on my multisite, at, and when going to , it shows the following error with the Pro Sites plugin:

Warning: array_keys() expects parameter 1 to be array, null given in /home/sophie36/public_html/wp-content/plugins/pro-sites/pro-sites-files/lib/ProSites/View/Front/Checkout.php on line 108

Thank You for your help.