Howto Hide 'admin' top-menu-bar when not logged-in?

Hi,

How to hide the top menu bar at https://box.mydomain.com/admin when not logged-in but shown when logged-in?

https://dl.dropboxusercontent.com/u/78930441/MiaB/howto-hide-admin-topmenu-bar.png

Note I know all changes in templates will be defaulted after each MiaB upgrade but I’m ready to assume the need to restore few customizations afterwards.

Thanks in advance,
Rgrds,