When try to modify x values of series it throws exception and hangs

java.lang.ClassCastException: java.lang.Double cannot be cast to java.lang.String
        at javafx.scene.chart.CategoryAxis.getDisplayPosition(CategoryAxis.java:61)
        at javafx.scene.chart.StackedBarChart.layoutPlotChildren(StackedBarChart.java:484)
        at javafx.scene.chart.XYChart.layoutChartChildren(XYChart.java:726)
        at javafx.scene.chart.Chart$1.layoutChildren(Chart.java:86)
        at javafx.scene.Parent.layout(Parent.java:1020)
        at javafx.scene.Scene.layoutDirtyRoots(Scene.java:582)
        at javafx.scene.Scene.doLayoutPass(Scene.java:553)
        at javafx.scene.Scene.access$3700(Scene.java:187)
        at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2309)
        at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:358)
        at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:560)
        at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:540)
        at com.sun.javafx.tk.quantum.QuantumToolkit$15.run(QuantumToolkit.java:425)
        at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:94)
        at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
        at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:101)
        at java.lang.Thread.run(Thread.java:724)