Install gir1.2-lightdm-1 by entering the following commands in the terminal:
sudo apt update sudo apt install gir1.2-lightdm-1
Description:
Typelib file for liblightdm-1
A GObject based library for LightDM clients to use to interface with LightDM.
Homepage: https://launchpad.net/lightdm
Version: 1.26.0-0ubuntu1
Section: universe/introspection