Bau_AdminPages::add_hooks(), which refers to the constant
WP_NETWORKS_ADMIN, is called during AJAX requests to wp-admin/includes/admin_ajax.php, in which case the constant is never defined. This can cause AJAX requests to return a notice if error reporting is on.
Changing line 491 of class_bau_admin_pages.php to
if (defined('WP_NETWORK_ADMIN') && WP_NETWORK_ADMIN) fixes the problem.