Comment 1 for bug 1388500

You can use the below .desktop file as a temporary fix and put it either in "~/.local/share/applications/" (your user only) or "/usr/share/applications/" (all users). You can edit the "Icon" and "Name" lines to your liking. It is possible that you may need to execute a "chmod +x" on the .desktop file.

[Desktop Entry]
Name=Authentication Dialog
Exec=/usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1
Icon=password
Terminal=false
Type=Application
StartupNotify=false
NoDisplay=true