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 ( oaTuple[i] == null )
				{
					continue;
				}
				boaFound[i] = true;
				if ( oaTuple[i] instanceof Number ) 
				
				{
					iaDataTypes[i] = IConstants.NUMERICAL;
				}
				else if ( oaTuple[i] instanceof String ) 
				
				{
					iaDataTypes[i] = IConstants.TEXT;
				}
				else if ( oaTuple[i] instanceof Date
						|| oaTuple[i] instanceof Calendar ) 
				
				
				{
					iaDataTypes[i] = IConstants.DATE_TIME;
				}
				for ( int j = 0; j < iColumnCount; j++ )
				{
					if ( !boaFound[j] )
					{
						bAllDone = false;
						break;
					}
				}