Steps to Reproduce

1. load the attached zul
2. click IE to drill down
3. click v6.0 to drill down again

Current Result

SEVERE:
java.lang.IndexOutOfBoundsException: Index: 5, Size: 5
at java.util.LinkedList.checkElementIndex(LinkedList.java:555)
at java.util.LinkedList.get(LinkedList.java:476)
at org.zkoss.chart.Series.getPoint(Series.java:378)
at org.zkoss.chart.ChartsEvent.getPoint(ChartsEvent.java:106)
at support.charts.pie.PieDrilldownComposer.lambda$doAfterCompose$0(PieDrilldownComposer.java:45)
at org.zkoss.zk.ui.AbstractComponent.onEvent(AbstractComponent.java:3162)
at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:3132)
at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:3074)
...

Expected Result

no error.

Debug Information

• this bug happens since 2.1.2-FL-20170619-Eval
• sIndex in au request is always 0, but it should be 1 after the first drill down
  dtid: z_5rc
  cmd_0: onPlotDrillDown
  uuid_0: dFDP1
  data_0: {"sIndex":0,"pIndex":9,"category":"v3.5"}
• Charts.service()

  			} else if (ChartsEvents.ON_PLOT_DRILL_DOWN.equals(cmd)) {
  				int sIndex = AuRequests.getInt(data, "sIndex", -1);
  				ChartsEvent evt = null;
  				if (sIndex == 0) {// first time drilldown
  					evt = ChartsEvent.getChartsEvent(request);
  				} else {
  					...
  				}