Bug 161222 Decoration label should be optional in Gantt Chart
It should not be mandatory to specify a decoration label for Gantt Charts, this can be left blank. Currently the UI and Engine enforce a data definition to be specified for it.
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/internal/datafeed/ResultSetWrapper.java
if ( bAllDone )
				{
					return;
				}
			}
		}
		logger.log( ILogger.WARNING,
				Messages.getString( "exception.resultset.data.type.retrieval.failed"  
				) );
	}
	/**
	 * Groups rows of data as specified in the grouping criteria for the series
	 * definition
	 * 
	 * @throws ChartException
	 */
	public void applyBaseSeriesSortingAndGrouping( SeriesDefinition sd,
			String[] saExpressionKeys ) throws ChartException
	{
		
		if ( bBaseGroupingApplied )
		{
			return;
		}
		bBaseGroupingApplied = true;
		boolean needBaseGrouping = true;
		
		final SeriesGrouping sg = sd.getGrouping( );
		if ( sg == null || !sg.isEnabled( ) )
		{