Bug 147263 Data can't be retrieved for extended item
Steps to reproduce: 1.Add a table in library 2.New a report, extend lib.table 3.Add a filter on table, choose "select value" Expected result: Available value will be listed Actual result: Error: The expression's value can not be retrieved. The DataSetHandle shouldn't be null.
data/org.eclipse.birt.report.data.adapter/src/org/eclipse/birt/report/data/adapter/impl/DataRequestSessionImpl.java
/*
	 * @see org.eclipse.birt.report.data.adaptor.impl.IDataRequestSession#getQueryResults(java.lang.String)
	 */
	public IQueryResults getQueryResults( String queryResultID )
			throws BirtException
	{
		return dataEngine.getQueryResults( queryResultID );
	}
	/*
	 * @see org.eclipse.birt.report.data.adaptor.impl.IDataRequestSession#clearCache(org.eclipse.birt.data.engine.api.IBaseDataSourceDesign,
	 *      org.eclipse.birt.data.engine.api.IBaseDataSetDesign)
	 */
	public void clearCache( IBaseDataSourceDesign dataSource,
			IBaseDataSetDesign dataSet ) throws BirtException
	{
		dataEngine.clearCache( dataSource, dataSet );
	}
	/*
	 * @see org.eclipse.birt.report.data.adaptor.impl.IDataRequestSession#prepare(org.eclipse.birt.data.engine.api.IQueryDefinition,
	 *      java.util.Map)
	 */
	public IPreparedQuery prepare( IQueryDefinition query, Map appContext )
			throws BirtException
	{
		return dataEngine.prepare( query, appContext );
	}
	/*
	 * @see org.eclipse.birt.report.data.adaptor.impl.IDataRequestSession#closeDataSource(java.lang.String)
	 */
	public void closeDataSource( String dataSourceName ) throws BirtException