SEVERE: 
java.lang.ArrayIndexOutOfBoundsException: 0
	at org.zkoss.zss.model.impl.chart.SeriesImpl.isXValueFomulaHidden(SeriesImpl.java:424)
	at org.zkoss.zssex.util.ChartsModelManager$PieModelSelector.toCharts(ChartsModelManager.java:161)
	at org.zkoss.zssex.util.ChartsModelManager.getChartsModel(ChartsModelManager.java:57)
	at org.zkoss.zssex.util.HighchartsHelper.drawCharts(HighchartsHelper.java:89)
	at org.zkoss.zssex.ui.widget.ChartsWidget.initChart(ChartsWidget.java:124)
	at org.zkoss.zssex.ui.widget.ChartsWidget.invalidate(ChartsWidget.java:119)
	at org.zkoss.zssex.ui.widget.DefaultWidgetHandler.updateWidget(DefaultWidgetHandler.java:102)
	at org.zkoss.zss.ui.Spreadsheet.updateWidget(Spreadsheet.java:3012)
	at org.zkoss.zss.ui.Spreadsheet.access$4600(Spreadsheet.java:232)
	at org.zkoss.zss.ui.Spreadsheet$InnerModelEventDispatcher.onChartContentChange(Spreadsheet.java:2664)
	at org.zkoss.zss.ui.Spreadsheet$InnerModelEventDispatcher.access$1500(Spreadsheet.java:2321)
	at org.zkoss.zss.ui.Spreadsheet$InnerModelEventDispatcher$9.onEvent(Spreadsheet.java:2378)
	at org.zkoss.zss.ui.ModelEventDispatcher.onEvent(ModelEventDispatcher.java:49)
	at org.zkoss.zss.model.impl.EventQueueListenerAdaptor$WrappedListener.onEvent(EventQueueListenerAdaptor.java:107)