Replace NaNs with zero because the XChart library has trouble with those:

java.lang.NumberFormatException
at java.math.BigDecimal.<init>(BigDecimal.java:459)
at java.math.BigDecimal.<init>(BigDecimal.java:728)
at java.math.BigDecimal.valueOf(BigDecimal.java:1054)
at com.xeiam.xchart.internal.chartpart.AxisTickBarChartCalculator.calculate(AxisTickBarChartCalculator.java:122)
at com.xeiam.xchart.internal.chartpart.AxisTickBarChartCalculator.<init>(AxisTickBarChartCalculator.java:48)
at com.xeiam.xchart.internal.chartpart.AxisTick.paint(AxisTick.java:77)
at com.xeiam.xchart.internal.chartpart.Axis.paint(Axis.java:240)
at com.xeiam.xchart.internal.chartpart.AxisPair.paint(AxisPair.java:147)
at com.xeiam.xchart.internal.chartpart.ChartPainter.paint(ChartPainter.java:110)
at com.xeiam.xchart.internal.chartpart.ChartPainter.paint(ChartPainter.java:70)
at com.xeiam.xchart.Chart.paint(Chart.java:94)
at com.xeiam.xchart.XChartPanel.paintComponent(XChartPanel.java:89)
Increase version number and rebuild.