Bug 136553 [regression]Preview error when set invalid group interval.
Description: Preview error when set invalid group interval. Steps to reproduce: 1. Insert a table 2. Add a group on number column, set interval to Year,1 3. Preview 4. Edit group on string column set interval to Prefix,1 5. Preview Expected result: Error msg about invalid group interval. Actual result: Error happened while running the report
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/DataPresentationEngine.java
context.registerBean( "row", new NativeRowObject( scope, rsets ) );
			
			DataEngineContext dteContext = DataEngineContext.newInstance(
					DataEngineContext.MODE_PRESENTATION, ctx.getSharedScope( ),
					reader, null );
			dteEngine = DataEngine.newDataEngine( dteContext );
		}
		catch ( Exception ex )
		{
			logger.log( Level.SEVERE, "can't create the DTE data engine", ex );
			ex.printStackTrace( );
		}
		this.reader = reader;
	}
	protected void doPrepareQuery( Report report, Map appContext )
	{
		
		queryIDMap.putAll( report.getQueryIDs( ) );
		loadDteMetaInfo( );
	}
	private void loadDteMetaInfo( )
	{
		DataInputStream dis = null;
		try
		{
			dis = new DataInputStream( reader.getStream( ReportDocumentConstants.DATA_META_STREAM ) );
			StringBuffer buffer = new StringBuffer( );
			while ( true )
			{
				String pRsetId = IOUtil.readString( dis );