Designer cannot delete the last RadioButtonGroup row

In the Window Designer, a newly added RadioButtonGroup always starts with one row ("Item 0"), and the Inspector's row editor refuses to delete the last remaining row. The delete button is disabled once the group is down to a single row, so an empty group cannot be created in the designer.

This conflicts with the documented and runtime behaviour of RadioButtonGroup: the constructor creates an empty group, RemoveAllRows() legally leaves zero rows, and a code-populated group (rows added at runtime, e.g. in Opening) is a standard pattern. The designer preview even renders a placeholder for an empty group, and generated code handles an empty group correctly. Other row-based designer controls (PopupMenu, ComboBox, ListBox) already allow zero rows.

Expected behaviour: the Inspector's row editor should allow deleting the last row of a RadioButtonGroup, and a new RadioButtonGroup should start empty like the other row-based controls.