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
{
					previewString = new NumberFormatter( isCustom( ) ? formatPattern
							: formatCategroy,
							ULocale.getDefault( ) ).format( 1234567890 );
				}
				else
				{
					previewString = new NumberFormatter( isCustom( ) ? formatPattern
							: formatCategroy,
							ULocale.getDefault( ) ).format( 123456789.01234 );
				}
			}
		}
		formatField.setText( displayFormat );
		previewLabel.setText( convertNullString( previewString ) );
		changeFormat.setEnabled( choiceSet != null );
	}
	private String convertNullString( String str )
	{
		if ( str == null )
		{
			return "";
		}
		return str;
	}
	private boolean containValue( SelectionChoice selectedChoice,
			String newValue, String property )
	{
		for ( Iterator iter = choiceList.iterator( ); iter.hasNext( ); )
		{