Because the fake {nav Switch User} item in the switcher UI counts as a session, the button
was always being shown. But if and when that changes and the fake item is no longer shown,
the {nav Switch User} button itself will stops being shown potentially locking out
non-logged-in users in multi-user computers where the only logged-in user has locked the
screen.
This patch drops the conditional check entirely and always shows the {nav Switch User"
button.