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
return displayName;
	}
	private String validateChoice( SelectionChoice choice, String displayLabel,
			String value )
	{
		String errorMessage = isValidValue( value );
		if ( errorMessage != null )
		{
			return errorMessage;
		}
		String newValue = convertToStandardFormat( value );
		if ( ( displayLabel == null && containValue( choice,
				newValue,
				COLUMN_DISPLAY_TEXT ) )
				|| ( containValue( choice, displayLabel, COLUMN_DISPLAY_TEXT ) ) )
		{
			return ERROR_MSG_DUPLICATED_LABEL;
		}
		if ( containValue( choice, newValue, COLUMN_VALUE ) )
		{
			return ERROR_MSG_DUPLICATED_VALUE;
		}
		return null;
	}
	private void changeDefaultValue( String value )
	{
		defaultValue = value;
		updateFormatField( );
		updateMessageLine( );
	}