sbbs

Since this script already sets an on_exit() handler to call uifc.bail()
it doesn't have to call it again (technically, before) in the "Done" block.
This results in "UIFC is unitialized" error displayed, as reported by
Fernando Toledo. Fixing issue #830

Set WIN_ESC (remains active, but greyed when ESC key pressed) mode flag
on main menu while we're here. That looks better.