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
{
			dataSetChooser.setItems( (String[]) dataSetList.toArray( new String[]{} ) );
			if ( StringUtil.isBlank( selectedDataSetName ) )
			{
				dataSetChooser.select( 0 );
				refreshColumns( false );
			}
			else
			{
				dataSetChooser.setText( selectedDataSetName );
			}
		}
	}
	private void refreshColumns( boolean onlyFilter )
	{
		if ( columnChooser == null )
		{
			return;
		}
		if ( !onlyFilter )
		{
			DataSetHandle dataSetHandle = inputParameter.getModuleHandle( )
					.findDataSet( dataSetChooser.getText( ) );
			try
			{
				columnList = DataUtil.getColumnList( dataSetHandle );
			}
			catch ( SemanticException e )
			{
				ExceptionHandler.handle( e );