Using php 7.0.17

When adding a new user with 'Activated by email' as 'Account status' I got the following errors:

Notice: Undefined index: reg_ip_min in /home/.../inc/users/model/_userlist.class.php on line 535
Notice: Undefined index: reg_ip_max in /home/.../inc/users/model/_userlist.class.php on line 535
Headers have already been sent in _userlist.class.php on line 535

However, the registration seems correct.