How do I get rid of this error

Warning: array_key_exists() expects parameter 2 to be array, null given in /home/content/52/6305152/html/build/wp-content/plugins/coursepress/includes/classes/class.shortcodes.php on line 2657

It appears when I try to add the sign-up to the menu and random other places.

http://www.nsadev.com/build