Stack Trace:

SEVERE: javafx.scene.control.Control loadSkinClass Failed to load skin
'StringProperty [bean: PopupButton@e9ac0f5[styleClass=menu-button
popup-button], name: skinClassName, value:
com.sun.javafx.scene.control.skin.MenuButtonSkin]' for control
PopupButton@e9ac0f5[styleClass=menu-button popup-button]
java.lang.IllegalArgumentException: argument type mismatch
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native
Method)
    at
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at javafx.scene.control.Control.loadSkinClass(Control.java:625)
    at javafx.scene.control.Control.access$700(Control.java:73)
    at javafx.scene.control.Control$5.invalidated(Control.java:560)
    at
javafx.beans.property.StringPropertyBase.markInvalid(StringPropertyBase.java:106)
    at
javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:140)
    at
com.sun.javafx.css.StyleableStringProperty.set(StyleableStringProperty.java:71)
    at javafx.scene.control.Control$5.set(Control.java:549)