ListBox ColumnWidths readback can be empty or lose percent widths

Reading ListBox.ColumnWidths after setting column widths can return inconsistent or incorrect values. In particular, reading immediately after ColumnCount/ColumnWidths setup may return an empty string, and percentage widths such as 4% or 22% can be returned as * instead of preserving the assigned width spec. This makes ColumnWidths unreliable as a read/write property.