Unable to add subsite.........

When I try to add a subsite I get this error:

Notice: Undefined variable: last_gateway in /home/digitals/public_html/wp-content/plugins/pro-sites/pro-sites.php on line 2075

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

Warning: Cannot modify header information - headers already sent by (output started at /home/digitals/public_html/wp-content/plugins/pro-sites/pro-sites.php:2075) in /home/digitals/public_html/wp-includes/pluggable.php on line 1228

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