Shows pointless confirmation message when lacking authority to shutdown

I added polkit restrictions preventing anybody from shutting down (using settings from http://askubuntu.com/a/454230/158442). As restrictions are added or removed, entries from the greeter's Shutdown confirmation dialog change. When there are no permissions, just the question is displayed, with no selectable options. I suggest that no message, or better yet, no menu item, be displayed if no permissions are present. (I have restricted shutdown permissions in a lab to prevent well-meaning students from unneccessarily shutting down PCs).

Release information:
Description: Ubuntu 14.04 LTS
Release: 14.04

Package information:
unity-greeter:
  Installed: 14.04.10-0ubuntu1
  Candidate: 14.04.10-0ubuntu1
  Version table:
 *** 14.04.10-0ubuntu1 0
        500 http://mirror.cse.iitk.ac.in/ubuntu/ trusty-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     14.04.9-0ubuntu1 0
        500 http://mirror.cse.iitk.ac.in/ubuntu/ trusty/main amd64 Packages