the attached example demostrates a NPE when using onPointClick events in combination with drilldown

2 sequences to create an NPE in this example:
1) click a category -> back (drill up) -> click same (or other) category again -> NPE
2) click a category -> click a sub category -> NPE

the NPE occurs when calling event.getPoint() in the event listener

in case one the event sent to the server indicate a problem on the client side when sending the event (might be a problem in highcharts or the ZK client side implementation)

dtid:z_nnz, cmd_0:onPlotClick, uuid_0:bU9Q1,
data_0:{"sIndex":0,"pIndex":1,"category":1}

dtid:z_nnz, cmd_0:onPlotClick, uuid_0:bU9Q1,
data_0:{"sIndex":1,"pIndex":1,"category":1}

in the second event the "sIndex" is incremented to 1 which leads to the NPE when retrieving the point from the event