Error Network Admin

First off, thanks for the great plugin.
We use it on a single site of an multisite installation. It works as intendend, but as soon as I try to enter the network admin area, we get a fatal error:

Fatal error: Uncaught Error: Call to undefined function wp_get_current_user() in /home/httpd/wp.kupf.at/wp-includes/capabilities.php:668 Stack trace: #0 /home/httpd/wp.kupf.at/wp-admin/network/settings.php(16): current_user_can('manage_network_...') #1 /home/httpd/wp.kupf.at/wp-content/plugins/admin-menu-groups/admin-menu-groups.php(15): require_once('/home/httpd/wp....') #2 /home/httpd/wp.kupf.at/wp-settings.php(377): include_once('/home/httpd/wp....') #3 /home/httpd/wp.kupf.at/wp-config.php(170): require_once('/home/httpd/wp....') #4 /home/httpd/wp.kupf.at/wp-load.php(37): require_once('/home/httpd/wp....') #5 /home/httpd/wp.kupf.at/wp-admin/admin.php(34): require_once('/home/httpd/wp....') #6 /home/httpd/wp.kupf.at/wp-admin/network/admin.php(13): require_once('/home/httpd/wp....') #7 /home/httpd/wp.kupf.at/wp-admin/network/plugin-install.php(15): require_once('/home/httpd/wp....') #8 {main} thrown in /home/httpd/wp.kupf.at/wp-includes/capabilities.php on line 668

Only thing to prevent this is to comment out the line require_once(“settings.php”);

Would be great, if you could take a look into this.
Thanks!