List "unknown" screens as well

There is also the possibility that the screen mapping by screenpool gets lost or partially lost ( like removal of plasmashellrc but not appletsrc) In this case if it was a multimonitor setup there will be containments assigned to a screen number which doesn't have a known connector. List them as well, marked as "Unknown 1" "Unknown 2" etc. This is an edge case of the edge case but it well possible it happens so it should be managed as well