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
dteResults = pQuery.execute( resultSet.getQueryResults( ),
						scope );
			}
			resultSet = new DteResultSet( dteResults, this, context );
			rsets.addFirst( resultSet );
			
			storeDteMetaInfo( pRsetId, rowId, queryID, dteResults.getID( ) );
			return resultSet;
		}
		catch ( BirtException be )
		{
			logger.log( Level.SEVERE, be.getMessage( ) );
			context.addException( be );
		}
		return null;
	}
	public void shutdown( )
	{
		rsets.clear( );
		if ( null != dos )
		{
			try
			{
				dos.close( );
			}
			catch ( IOException e )
			{
			}