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
selectionChioceList.setValue( null );
			if ( isStatic( ) )
			{
				
				inputParameter.setValueType( DesignChoiceConstants.PARAM_VALUE_TYPE_STATIC );
				if ( !DesignChoiceConstants.PARAM_CONTROL_TEXT_BOX.equals( newControlType )
						&& !DesignChoiceConstants.PARAM_CONTROL_CHECK_BOX.equals( newControlType ) )
				{
					for ( Iterator iter = choiceList.iterator( ); iter.hasNext( ); )
					{
						SelectionChoice choice = (SelectionChoice) iter.next( );
						if ( isValidValue( choice.getValue( ) ) == null )
						{
							selectionChioceList.addItem( choice );
						}
					}
				}
				inputParameter.setDataSetName( null );
				inputParameter.setValueExpr( null );
				inputParameter.setLabelExpr( null );
			}
			else
			{
				
				inputParameter.setValueType( DesignChoiceConstants.PARAM_VALUE_TYPE_DYNAMIC );
				inputParameter.setDataSetName( dataSetChooser.getText( ) );
				inputParameter.setValueExpr( getExpression( columnChooser.getText( ) ) );
				
				
				if ( displayTextChooser.getText( ).equals( "<None>" ) )