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
{
		String type = getSelectedDataType( );
		if ( type.equals( lastDataType ) )
		{
			return;
		}
		if ( buildControlTypeList( type ) )
		{
			changeControlType( );
		}
		lastDataType = type;
		initFormatField( );
		if ( isStatic( ) )
		{
			makeUniqueAndValid( );
			refreshValueTable( );
		}
		else
		{
			refreshColumns( true );
		}
		updateMessageLine( );
	}
	private boolean buildControlTypeList( String type )
	{
		String[] choices;
		if ( isStatic( ) )
		{
			if ( DesignChoiceConstants.PARAM_TYPE_BOOLEAN.equals( type ) )
			{