Bug 139346 Using isTopN in table inside list group header doesn't work.
Description: Using isTopN in table inside list group header doesn't work. Steps to reproduce: 1.Insert a list with a group 2.Insert a table to list group header 3.Using Total.isTopN(row[],2,null,0) as filter expression in table item. 4.Preview Result: Only the first group displayed top 2 records, other groups kept display all records.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/QueryExecutor.java
{
    		dataSet.afterClose();
		}
	    catch (DataException e )
		{
			logger.logp( Level.FINE,
						QueryExecutor.class.getName( ),
						"close",
						e.getMessage( ),
						e );
		}
	    dataSet = null;
		dataSource = null;
	    
		logger.logp( Level.FINER,
				QueryExecutor.class.getName( ),
				"close",
				"executor closed " );
	}
	/*
	 * @see org.eclipse.birt.data.engine.impl.IQueryExecutor#getDataSet()
	 */
	public DataSetRuntime getDataSet( )
	{
		return dataSet;
	}
	
	/*
	 * @see org.eclipse.birt.data.engine.impl.IQueryExecutor#getSharedScope()
	 */