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
{
			ResultSetColumnHandle cachedColumn = (ResultSetColumnHandle) iter.next( );
			if ( DEUtil.getExpression( cachedColumn ).equals( expression ) )
			{
				return cachedColumn.getColumnName( );
			}
		}
		
		return expression;
	}
	private String getInputControlDisplayName( )
	{
		String type = getInputControlType( );
		String displayName = null;
		if ( CONTROL_TYPE_CHOICE_SET.findChoice( type ) != null )
		{
			displayName = CONTROL_TYPE_CHOICE_SET.findChoice( type )
					.getDisplayName( );
		}
		else
		{
			if ( PARAM_CONTROL_COMBO.equals( type ) )
			{
				displayName = DISPLAY_NAME_CONTROL_COMBO;
			}
			else if ( PARAM_CONTROL_LIST.equals( type ) )
			{
				displayName = DISPLAY_NAME_CONTROL_LIST;
			}
		}