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
dialog.setInput( choice );
			dialog.setValidator( new SelectionChoiceDialog.ISelectionChoiceValidator( ) {
				public String validate( String displayLabel, String value )
				{
					return validateChoice( choice, displayLabel, value );
				}
			} );
			if ( dialog.open( ) == Dialog.OK )
			{
				choice.setValue( convertToStandardFormat( choice.getValue( ) ) );
				if ( isDefault )
				{
					changeDefaultValue( choice.getValue( ) );
				}
				return true;
			}
			return false;
		}
		public boolean newItem( )
		{
			SelectionChoice choice = StructureFactory.createSelectionChoice( );
			SelectionChoiceDialog dialog = new SelectionChoiceDialog( Messages.getString( "ParameterDialog.SelectionDialog.New" ) ); 
			dialog.setInput( choice );
			dialog.setValidator( new SelectionChoiceDialog.ISelectionChoiceValidator( ) {
				public String validate( String displayLabel, String value )
				{
					return validateChoice( null, displayLabel, value );
				}
			} );
			if ( dialog.open( ) == Dialog.OK )