Bug 121687 Exception throws when export data in table which inside a grid cell.
Description: Exception throws when export data in table which inside a grid cell. Steps to reproduce: 1. insert a grid. 2. insert one table to one grid cell. 3. insert another table to the other grid cell. 4. export data in two tables. Expected result: Data are exported. Actual result: Exception in: ReportEngineService.getMetaData( )
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/DataExtractionTask.java
queryResultName = parId.getDataSetName();
				}
				assert queryResultName != null;
				
				IQueryResults parentQueryResult = dataEngine
						.getQueryResults( queryResultName );
				assert parentQueryResult != null;
				
				IResultIterator iter = parentQueryResult.getResultIterator( );
				long rowid = dataSetId.getRowID( );
				
				int i = 0;
				while ( iter.next( ) && i++ < rowid ) 		;
				
				IResultIterator subIter = iter.getSecondaryIterator( dataSetId
						.getQueryName( ), executionContext.getScope( ) );
				
				ExtractionResults results = new ExtractionResults( subIter, 
						selectedColumns, query.getRowExpressions() );
				
				resultMetaList.add( results.getResultMetaData());
				return results;
			}
			catch( BirtException be )
			{
				be.printStackTrace( );
			}
		}
		
		return null;