Bug 123219 Export data in attached file which has a table covers multiple page will throw exception.
Description: Export data in attached file which has a table covers multiple page will throw exception. Steps to reproduce: 1. Preview attached design file in viewer. 2. Select the table and click Export Data Expected result: No errors. Actual result: Exception Exception in: ReportEngineService.getMetaData( )
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/DataExtractionTask.java
{
			IBaseQueryDefinition query = (IBaseQueryDefinition)mapResultSetNameToQuery
									.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();