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
private Combo dataSetChooser, columnChooser, displayTextChooser;
	
	private Label previewLabel;
	private TableViewer valueTable;
	private String lastDataType, lastControlType;
	private String formatCategroy, formatPattern;
	private String defaultValue;
	private Composite valueArea;
	private List columnList;
	private IStructuredContentProvider contentProvider = new IStructuredContentProvider( ) {
		public void dispose( )
		{
		}
		public void inputChanged( Viewer viewer, Object oldInput,
				Object newInput )
		{
		}
		public Object[] getElements( Object inputElement )
		{
			ArrayList list = ( (ArrayList) inputElement );
			ArrayList elementsList = (ArrayList) list.clone( );
			return elementsList.toArray( );
		}
	};
	private ITableLabelProvider labelProvider = new ITableLabelProvider( ) {
		public Image getColumnImage( Object element, int columnIndex )
		{
			if ( valueTable.getColumnProperties( ).length == 4
					&& columnIndex == 1 )