Fix bug: https://bugs.kde.org/show_bug.cgi?id=341163

This requires checking the greeter API in https://github.com/sddm/sddm

then fixing the code in:

plasma-workspace/lookandfeel/contents/loginmanager/

There is a readme.txt in that folder which shows an easier way to test without having to log out to test. 

Requires a working Plasma 5 setup and some coding and debugging skills.