I'm running GNOME 3.7.92 from a live CD for the Fedora test day. I started creating new user accounts with various settings to see if I could break anything. I set one of the new accounts to "Administrator" instead of "Standard", left him on "Account Disabled", and did something to get the panel locked (whether leaving the panel, or closing Settings, or just clicking the toggle, I don't remember). This is the only "Administrator" account on my system. Now, when I try to do anything that requires authentication, polkit prompts for this users's password, even though he has none set. Blank passwords are rejected, so I cannot log in.

I then set a password for the root user (since this was a live session) by using passwd directly, hoping both to simulate a more typical scenario where root has a password, and that I'd then be prompted for the root password instead of this user's nonexistent password. No such luck - polkit still wants a password for my throwaway, passwordless user.  If I didn't know how to use passwd to fix this, I'd never be able to perform administrative actions again.

After manually setting a password for this user with passwd, I was obviously able to authenticate as him without issues. I then changed his password type to "login without password" and closed Settings. With an admin set to login without a password I was able to perform privileged actions without any authentication at all, which makes sense for this scenario, so the problem only exists if the account is left as "account disabled."