unlock xubuntu locked by guest, when no password accepted

To remove guest user in xubuntu, that causes input password after wake up:
create new file with:

$ sudo vim /etc/lightdm/lightdm.conf.d/50-my-custom-config.conf


 [SeatDefaults]
allow-guest=false

close all desktop apps, restart lightdm:

$ sudo service lightdm restart


It was really strange. that guest user is turned on by default in xubuntu.

Reasons to remove guest:
- security issue
- just inconvenient, it is just not possible to login after wake, because temporary guest user asking for password, and don't accept default user password.

references: got original receipt there, just more details in this manual:
http://www.webupd8.org/2014/08/lightdm-how-to-disable-user-list-or.html

Another required step to avoid locking under lightdm user is:

$ sudo apt-get remove gnome-screensaver

and setup locker usage
$ light-locker-settings