Run the application, click the button.

Exception :
java.lang.NullPointerException
at com.sun.javafx.scene.control.skin.TableViewSkinBase$3.invalidated(TableViewSkinBase.java:152)
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:339)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(ObjectPropertyBase.java:103)
at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:110)
at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:143)
at javafx.css.StyleableObjectProperty.set(StyleableObjectProperty.java:82)
at javafx.css.StyleableObjectProperty.applyStyle(StyleableObjectProperty.java:68)
at javafx.scene.CssStyleHelper.resetToInitialValues(CssStyleHelper.java:374)
at javafx.scene.CssStyleHelper.createStyleHelper(CssStyleHelper.java:92)
at javafx.scene.Node.impl_processCSS(Node.java:8479)
at javafx.scene.Parent.impl_processCSS(Parent.java:1179)
at javafx.scene.control.Control.impl_processCSS(Control.java:861)
at javafx.scene.Node.processCSS(Node.java:8407)
at javafx.scene.Node.processCSS(Node.java:8400)
at javafx.scene.Scene.doCSSPass(Scene.java:512)
at javafx.scene.Scene.access$3600(Scene.java:187)
at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2293)
at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:372)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:561)
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:722)