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
clearArea( valueArea );
		lastControlType = null;
		if ( isStatic( ) )
		{
			switchToStatic( );
		}
		else
		{
			switchToDynamic( );
		}
		buildControlTypeList( getSelectedDataType( ) );
		valueArea.layout( );
		initValueArea( );
		updateCheckBoxArea( );
	}
	private void switchToCheckBox( )
	{
		createLabel( valueArea, LABEL_DEFAULT_VALUE );
		defaultValueChooser = new Combo( valueArea, SWT.READ_ONLY | SWT.BORDER );
		defaultValueChooser.add( CHOICE_NO_DEFAULT );
		defaultValueChooser.add( BOOLEAN_TRUE );
		defaultValueChooser.add( BOOLEAN_FALSE );
		defaultValueChooser.setLayoutData( new GridData( GridData.FILL_HORIZONTAL ) );
		defaultValueChooser.addSelectionListener( new SelectionAdapter( ) {
			public void widgetSelected( SelectionEvent e )
			{
				switch ( defaultValueChooser.getSelectionIndex( ) )
				{
					case 0 :
						defaultValue = null;