Bug 208419 NullPointerException at CubeResultSet close
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/DataInteractiveEngine.java
keyBuffer.append( "." );
					keyBuffer.append( rowId );
					keyBuffer.append( "." );
					keyBuffer.append( queryId );
					rsetId = (String) rsetRelations.get( keyBuffer.toString( ) );
				}
			}
		}
		return rsetId;
	}
	protected void doPrepareQuery( Report report, Map appContext )
	{
		this.appContext = appContext;
		
		queryIDMap.putAll( report.getQueryIDs( ) );
	}
	
	protected IBaseResultSet doExecuteQuery( IBaseResultSet parentResult,
			IQueryDefinition query, boolean useCache )
	{
		String queryID = (String) queryIDMap.get( query );
		try
		{
			IBaseQueryResults parentQueryResults = null;
			if ( parentResult != null )
			{
				parentQueryResults = parentResult.getQueryResults( );
			}
			
			String resultSetID = loadResultSetID( parentResult, queryID );