java.lang.NullPointerException
        at javafx.scene.chart.PieChart.resolveCollision(PieChart.java:515)
        at javafx.scene.chart.PieChart.layoutChartChildren(PieChart.java:471)
        at javafx.scene.chart.Chart$1.layoutChildren(Chart.java:58)
        at javafx.scene.Parent.layout(Parent.java:900)
        at javafx.scene.Scene.layoutDirtyRoots(Scene.java:451)
        at javafx.scene.Scene.doLayoutPass(Scene.java:424)
        at javafx.scene.Scene.access$2800(Scene.java:132)
        at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:1750)
        at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:292)
        at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:398)
        at com.sun.javafx.tk.quantum.QuantumToolkit$10.run(QuantumToolkit.java:330)
        at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
        at com.sun.glass.ui.win.WinApplication$2$1.run(WinApplication.java:62)
        at java.lang.Thread.run(Thread.java:662)