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
baseReference = ChartUtil.stringValue( ( (Object[]) resultSet.get( iStartIndex ) )[iBaseColumnIndex] );
			}
			Object[] oaTuple, oaSummarizedTuple = null;
			int iGroupIndex = 0, iLastGroupIndex = 0, iGroupCounter = 0;
			boolean bFirst = true, bGroupBreak = false;
			List trashList = new ArrayList( );
			for ( int j = iStartIndex; j < iEndIndex; j++ )
			{
				oaTuple = (Object[]) resultSet.get( j );
				if ( oaTuple[iBaseColumnIndex] != null )
				{
					String dBaseValue = String.valueOf( oaTuple[iBaseColumnIndex] );
					if ( !dBaseValue.equals( baseReference ) )
					{
						iGroupCounter++;
						baseReference = dBaseValue;
					}
					if ( iGroupCounter > iGroupingInterval )
					{
						iGroupIndex++;
					}
				}
				else
				{
					
					if ( baseReference != null )
					{
						iGroupCounter++;
						baseReference = null;
					}