Log off entry appears in ReactOS Login Window Shutdown Prompt, without any username

Issue: When using the LiveCD and you log off the system, you will be taken to the standard "Log onto ReactOS" prompt. However, should one wish to Shutdown or Restart the system from that prompt, they will notice a strange "Log off """ (two quotes with nothing between them).

Resolution: Add a boolean or condition that checks if the system is logged off. If it is, disable that "Log off..." menu entry appearing in the "Shut Down ReactOS" window.

Versions affected: 0.5 SVN, likely 0.4 as well. Confirmed to be noticeable on the LiveCD build of ReactOS.