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/DataGenerationEngine.java
logger.log( Level.SEVERE, "can't create the DTE data engine", ex );
			ex.printStackTrace( );
		}
		try
		{
			dos = new DataOutputStream( writer
					.createRandomAccessStream( ReportDocumentConstants.DATA_META_STREAM ) );
		}
		catch ( IOException e )
		{
			logger.log( Level.SEVERE, e.getMessage( ) );
			e.printStackTrace( );
		}
	}
	protected void doPrepareQuery( Report report, Map appContext )
	{
		
		queryIDMap.putAll( report.getQueryIDs( ) );
		for ( int i = 0; i < report.getQueries( ).size( ); i++ )
		{
			IQueryDefinition queryDef = (IQueryDefinition) report.getQueries( )
					.get( i );
			try
			{
				IPreparedQuery preparedQuery = dteEngine.prepare( queryDef,
						appContext );
				queryMap.put( queryDef, preparedQuery );
			}
			catch ( BirtException be )
			{