Bug 141950 Selection of select value in data set filter is error
Details: Selection of select value in data set filter is error Step: 1.New a report design. 2.Create a sample datasource and dataset. 3.Switch to filter. 4.Select a value in expression. 5.Drop the list of the value1 and select <select value...> Actual result: No value is appear and pop up an error. It said that "An expression has not been set"
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/data/ui/util/DataSetProvider.java
*/
	public DataRequestSession getDataRequestSession( DataSetHandle dataSet )
			throws BirtException
	{
		if ( sessionTable.get( dataSet.getName( ) ) != null )
			return (DataRequestSession) sessionTable.get( dataSet.getName( ) );
		else
		{
			DataSessionContext context = new DataSessionContext( DataSessionContext.MODE_DIRECT_PRESENTATION,
					dataSet.getModuleHandle( ) );
			DataRequestSession session = DataRequestSession.newSession( context );
			sessionTable.put( dataSet.getName( ), session );
			return session;
		}
	}
	
	/**
	 * @param dataSet
	 * @return
	 * @throws BirtException
	 */
	public Collection getParametersFromDataSet( DataSetHandle dataSet )
			throws BirtException
	{
		return prepareQuery( dataSet ).getParameterMetaData( );
	}
	
	/**
	 * 
	 * @param dataSet