Broken

Installed the latest version of the plugin and upon activation I received a PHP error:

Notice: Undefined variable: srff_domain in /Users/username/Sites/californianative/app/plugins/refer-a-friend-program-for-woocommerce/storeya-refer-a-friend.php on line

https://ww.wp.xz.cn/plugins/refer-a-friend-program-for-woocommerce/