Bug 166315 Combo box doesn't allow blank when set string type in parameter editor
Combo box doesn't allow blank when set string type in parameter editor Steps to reproduce: 1.New a parameter, display type is Combo Box 2.Select data type as String Expected result: "Allow blank values" is enable. Actual result: "Allow blank values" is gray and can't be checked.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ParameterDialog.java
&& columnIndex == 1 )
			{
				SelectionChoice choice = ( (SelectionChoice) element );
				if ( isDefaultChoice( choice ) )
				{
					return DEFAULT_ICON;
				}
			}
			return null;
		}
		public String getColumnText( Object element, int columnIndex )
		{
			SelectionChoice choice = ( (SelectionChoice) element );
			final int valueIndex = valueTable.getColumnProperties( ).length - 2;
			String text = null;
			if ( valueTable.getColumnProperties( ).length == 4
					&& columnIndex == 1 )
			{
				if ( isDefaultChoice( choice ) )
				{
					text = FLAG_DEFAULT;
				}
			}
			else if ( columnIndex == valueIndex )
			{
				text = choice.getValue( );
			}
			else if ( columnIndex == valueIndex + 1 )
			{
				text = choice.getLabel( );