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
* @param dataSource
	 * @return
	 * @throws BirtException
	 */
	public IBaseDataSourceDesign createDataSourceDesign(
			DataSourceHandle dataSource ) throws BirtException
	{
		DataSessionContext context = new DataSessionContext( DataSessionContext.MODE_DIRECT_PRESENTATION,
				dataSource.getModuleHandle( ) );
		DataRequestSession session = DataRequestSession.newSession( context );
		return session.getModelAdaptor( ).adaptDataSource( dataSource );
	}
	
	/**
	 * Get cached data set item model. If none is cached, return null;
	 * 
	 * @param ds
	 * @param columns
	 */
	public DataSetViewData[] getCachedDataSetItemModel( DataSetHandle ds )
	{
		DataSetViewData[] result = (DataSetViewData[]) this.htColumns.get( ds );
		if ( result == null )
			result = new DataSetViewData[0];
		return result;
	}
	
	/**
	 * 
	 * @param ds