Bug 190769 [Regression]The attached report pop up exception when preview
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/QueryResultSet.java
public QueryResultSet( QueryResultSet parent,
			ISubqueryDefinition queryDefn, IResultIterator ri ) 
	{
		assert parent != null;
		assert queryDefn != null;
		this.parent = parent;
		this.id = new DataSetID( parent.getID( ), parent.getRowIndex( ),
				queryDefn.getName( ) );
		this.context = parent.context;
		this.dataEngine = parent.dataEngine;
		this.queryDefn = queryDefn;
		this.rs = ri;
		this.queryResults = new SubQueryResults( rs );
		initializeRowIdOfGroups( queryDefn.getGroups( ).size( ) );
	}
	private void initializeRowIdOfGroups( int groupCount )
	{
		this.rowIdOfGroups = new long[groupCount + 2];
	}
	private int getGroupCount( )
	{
		if ( queryDefn instanceof IQueryDefinition )
		{
			List groups = ( (IQueryDefinition) queryDefn ).getGroups( );
			assert groups != null;
			return groups.size( );
		}
		return 0;
	}