clearing a chart model causes an IndexOutOfBoundsException

the example shows a stacked area chart with dynamic content updated in 2 ways

1 replace the whole model with a new one "replace model"
2 clear the existing model and fill with new data "update same model"

both operations fail
1 possibly a duplicate of ZKCHARTS-2
2 causes an IndexOutOfBoundsException in SimpleCategoryModel::clear()

SEVERE:
java.lang.IndexOutOfBoundsException: Index: -1, Size: 2
at java.util.LinkedList.entry(LinkedList.java:365)
at java.util.LinkedList.get(LinkedList.java:315)
at org.zkoss.chart.PlotData.getSeries(PlotData.java:341)
at org.zkoss.chart.Charts.getSeries(Charts.java:1819)
at org.zkoss.chart.Charts$MyChartDataListener.onChange(Charts.java:472)
at org.zkoss.zul.AbstractChartModel.fireEvent(AbstractChartModel.java:55)
at org.zkoss.zul.SimpleCategoryModel.clear(SimpleCategoryModel.java:157)
...