Enumerated Value List - How to unselect a previously selected value
I created a new attribute for one object type in Windchill and then added an enumerated value list constraint to it with two values.
Modifying this object in Windchill now gives me the option to leave this property undefined (unset) or select one of the two list values.
Selecting either of the values works fine, and switching between the values works fine, but I can't figure out how to go back to blank (undefined). Even though there is a blank value displayed, attempting to return to pick it (after having previously selected a different value) is not being permitted. Windchill just throws an error:
Is there any way around this? I don't really want an extra "None" entry in my list because "None" and undefined are not the same thing and won't return the same results in a search.

