UI.SelectModelElementsData returns categories when no selection made

[andydandy74]

Buttons of the uiselectelementsofcat class will return the categories of their category filter if no model element has been selected. It would be preferable if they returned null (single element selection) or an empty list (multi-element selection). One approach may be to check all button tags in setclose if they contain Revit categories and remove them.

[MostafaElAyoubi]

That would indeed be a good approach since buttons should never return categories. I'll take care of it publish it in the next version along with all the great stuff you contributed.