Bug 317267 [Automation][Regression]Error is thrown out when preview gantt type chart
chart/org.eclipse.birt.chart.engine.extension/src/org/eclipse/birt/chart/extension/datafeed/GanttDataSetProcessorImpl.java
ChartException.DATA_SET,
					uiex );
		}
		if ( dsi.size( ) == 0 )
		{
			throw new ChartException( ChartEngineExtensionPlugin.ID,
					ChartException.DATA_SET,
					"exception.empty.dataset", 
					Messages.getResourceBundle( getULocale( ) ) );
		}
		GanttEntry gde;
		CDateTime[] cala = new CDateTime[2];
		CDateTime calMax = null;
		while ( dsi.hasNext( ) )
		{
			gde = (GanttEntry) dsi.next( );
			if ( gde != null )
			{
				cala[0] = gde.getStart( );
				cala[1] = gde.getEnd( );
				for ( int j = 0; j < 2; j++ )
				{
					if ( cala[j] == null )
						continue;
					if ( calMax != null )
					{
						if ( calMax.before( cala[j] ) )
						{
							calMax = cala[j];
						}