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
catch ( BirtException e )
			{
			}
		}
		return string;
	}
	private String convertToStandardFormat( Date date )
	{
		if ( date == null )
		{
			return null;
		}
		return new DateFormatter( STANDARD_DATE_TIME_PATTERN, ULocale.US ).format( date );
	}
	private String getExpression( String columnName )
	{
		for ( Iterator iter = columnList.iterator( ); iter.hasNext( ); )
		{
			ResultSetColumnHandle cachedColumn = (ResultSetColumnHandle) iter.next( );
			if ( cachedColumn.getColumnName( ).equals( columnName ) )
			{
				return DEUtil.getExpression( cachedColumn );
			}
		}
		
		return columnName;
	}
	private String getColumnName( String expression )
	{
		for ( Iterator iter = columnList.iterator( ); iter.hasNext( ); )