lightdm crashes with no input devices

[Michal Suchanek]

According to this report https://github.com/systemd/systemd/issues/6219 when the udev file which identifies devices as keyboards and mice was not installed due to bug in installation script lightdm crashed on start.

On many systems you always have power button present as keyboard so this never happens but some systems may have no built-in input devices and when no external input device is connected lightdm could crash on such system.

[Michal Suchanek (hramrach)]

This is supposed to happen when line containing IMPORT{builtin}="input_id" is removed from /lib/udev/rules.d

I am unable to reproduce with 1.22.0 which is supposedly the same as Fedora 26 has. So this may be specific to a particular greeter or not reproducible at all outside of that particular system/distro.