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
{
			return;
		}
		
		final String sFunctionName = sg.getAggregateExpression( );
		final int iOrthogonalSeriesCount = saExpressionKeys.length;
		IAggregateFunction[] iafa = new IAggregateFunction[iOrthogonalSeriesCount];
		try
		{
			for ( int i = 0; i < iOrthogonalSeriesCount; i++ )
			{
				iafa[i] = PluginSettings.instance( )
						.getAggregateFunction( sFunctionName );
				iafa[i].initialize( );
			}
		}
		catch ( ChartException pex )
		{
			throw new ChartException( ChartEnginePlugin.ID,
					ChartException.DATA_BINDING,
					pex );
		}
		final DataType dtGrouping = sg.getGroupType( );
		if ( dtGrouping == DataType.NUMERIC_LITERAL )
		{
			groupNumerically( workingResultSet,
					iSortColumnIndex,
					saExpressionKeys,
					iaGroupBreaks,
					null,