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
}
		else
		{
			doNotEcho.setEnabled( false );
		}
		
		if ( DesignChoiceConstants.PARAM_CONTROL_TEXT_BOX.equals( getSelectedControlType( ) )
				|| DesignChoiceConstants.PARAM_CONTROL_CHECK_BOX.equals( getSelectedControlType( ) ) )
		{
			needSort.setEnabled( false );
		}
		else
		{
			needSort.setEnabled( true );
		}
	}
	private void updateMessageLine( )
	{
		String errorMessage = validateName( );
		if ( errorMessage == null )
		{
			if ( !isStatic( )
					&& columnChooser != null
					&& columnChooser.getItemCount( ) == 0 )
			{
				errorMessage = ERROR_MSG_NO_AVAILABLE_COLUMN;
			}
			else if ( defaultValue == null
					&& ( PARAM_CONTROL_COMBO.equals( getSelectedControlType( ) ) || DesignChoiceConstants.PARAM_CONTROL_RADIO_BUTTON.equals( getSelectedControlType( ) ) ) )
			{