Bug 124251 the data cann't been exported.
Description: the data cann't been exported. Steps to reproduce: 1. new a report 2. new a datasource and a data set(DS_A) 3. use an external library 4. drag a table to the report layout from the imported library 5. insert an another table into the layout of the report and bind the data set(DS_A) 6. preview in the 'Web Viewer' and export the data Actual result: The data can been exported. Expect result: The data can been exporteded
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/DataExtractionTask.java
.get( resultSetName );
			assert query != null;
			validateSelectedColumns( query );
			
			IQueryResults queryResults = dataEngine.getQueryResults( resultSetName );
			assert queryResults.getResultIterator() != null;
			 
			currentResult = new ExtractionResults( queryResults.getResultIterator() 
					, selectedColumns, getValueExpressions( query ) );
			return currentResult;
		}
		catch ( BirtException e )
		{
			e.printStackTrace( );
		}
		return null;
	}
	
	/*
	 * data export by report item instance
	 */
	private IExtractionResults extractByInstanceId( ) throws EngineException
	{
		assert instanceId != null;
		
		assert executionContext.getDataEngine() != null;
		DataEngine dataEngine = executionContext.getDataEngine().getDataEngine();
		
		ReportItemDesign rptItem = (ReportItemDesign) report
				.getReportItemByID( instanceId.getComponentID( ) );