Throw a exception when points in SChartColumnSeries is touched


I have downlaod the example projects and tried, and found a problem. I ran the HandlingSelection project, it worked well, but I changed the code

lineSeries.selectionMode = SChartSelectionPoint;

then the APP throw an Exception everytime when I touched the Mushrooms of 2013.

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSMutableOrderedSet addObject:]: object cannot be nil'
*** First throw call stack: