Error on Registration

I’m getting a critical error message on this site when people try to register, and then a follow up from WordPress with this information.

Error Details
=============
An error of type E_ERROR was caused in line 741 of the file /nas/content/live/diacmin/wp-content/plugins/new-user-approve/new-user-approve.php. Error message: Uncaught Error: Call to a member function get_error_code() on null in /nas/content/live/diacmin/wp-content/plugins/new-user-approve/new-user-approve.php:741
Stack trace:
#0 /nas/content/live/diacmin/wp-includes/class-wp-hook.php(289): pw_new_user_approve->show_user_pending_message(NULL)
#1 /nas/content/live/diacmin/wp-includes/plugin.php(212): WP_Hook->apply_filters(NULL, Array)
#2 /nas/content/live/diacmin/wp-includes/user.php(2768): apply_filters(‘registration_er…’, Object(WP_Error), ‘James Bosma’, ‘james.bosma@g…’)
#3 /nas/content/live/diacmin/wp-login.php(1086): register_new_user(‘James Bosma’, ‘james.bosma@g…’)
#4 {main}
thrown

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