Bug 153405 Null parameter value is inconsistent between designer and preview
Description: Null parameter value is inconsistent between designer and preview Steps to reproduce: 1. New a report parameter, list-box, tick AllowNull. 2. Click New button, click OK without input anything. 3. Drag the parameter to Layout and preview Actual result: After step2, display text is "Null" and value is empty. However, when preview, the display text is "Null Value". Expected result: Display text and value should be consistent between Edit Parameter Dialog in Layout and Parameter dialog during preview.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ParameterDialog.java
{
				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( );
				if ( text == null )