fp.bugs: 2981 - single item selection in lists should disallow deselect state.

>From: ###@###.### (Robert Uomini)

"In a List object created with multiple-selections = false,
a list item may be toggled between the selected- and unselected state.
This is correct operation for a multiple-selection List but not for a
single-selection one. It can be a problem if the application expects there
to always be a selected item."

Robert Uomini

While there is a simple workaround of just checking for no selected item,
I agree with Robert that this should probably be built into the list class
to make it cleaner when writing apps.

Vijay