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
else if ( obj instanceof Date )
				{
					baseReference = new CDateTime( (Date) obj );
				}
				else
				{
					
					baseReference = new CDateTime( 0 );
				}
			}
			if ( iGroupingInterval != 0 )
			{
				
				baseReference.clearBelow( cunit );
			}
			lastReference = (CDateTime) baseReference.clone( );
			Object[] oaTuple, oaSummarizedTuple = null;
			int iGroupIndex = 0, iLastGroupIndex = 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 )
				{
					CDateTime dCurrentValue = null;
					Object obj = oaTuple[iBaseColumnIndex];
					
					if ( obj instanceof CDateTime )
					{