NPE when a scene property listener invokes Node.impl_processCSS()

I put a listener on Node.sceneProperty() which invokes:
    - Node.impl_processCSS()
    - Parent.layout()

When my scene graph is connect to the my scene, the listener is executed.
It crashes with the following stack trace below.

After discussing with David and Martin, it seems it is a bug in the scene graph layer.



Caused by: java.lang.NullPointerException
at javafx.scene.Scene$MouseHandler.access$8200(Scene.java:3336)
at javafx.scene.Scene.generateMouseExited(Scene.java:3333)
at javafx.scene.Parent$2.onProposedChange(Parent.java:492)
at com.sun.javafx.collections.VetoableListDecorator.clear(VetoableListDecorator.java:258)
at com.sun.javafx.scene.control.skin.SliderSkin.setShowTickMarks(SliderSkin.java:184)
at com.sun.javafx.scene.control.skin.SliderSkin.initialize(SliderSkin.java:93)
at com.sun.javafx.scene.control.skin.SliderSkin.<init>(SliderSkin.java:71)
at javafx.scene.control.Slider.createDefaultSkin(Slider.java:635)
at javafx.scene.control.Control.impl_processCSS(Control.java:866)
at javafx.scene.Parent.impl_processCSS(Parent.java:1228)
at javafx.scene.Parent.impl_processCSS(Parent.java:1228)
at javafx.scene.Parent.impl_processCSS(Parent.java:1228)
at javafx.scene.Parent.impl_processCSS(Parent.java:1228)
at javafx.scene.Parent.impl_processCSS(Parent.java:1228)
at javafx.scene.Parent.impl_processCSS(Parent.java:1228)
at javafx.scene.Parent.impl_processCSS(Parent.java:1228)
at javafx.scene.Parent.impl_processCSS(Parent.java:1228)
at javafx.scene.control.Control.impl_processCSS(Control.java:870)
at javafx.scene.Node.processCSS(Node.java:8587)
at javafx.scene.Node.impl_processCSS(Node.java:8632)
at com.oracle.javafx.scenebuilder.kit.metadata.util.Deprecation.processCSS(Deprecation.java:64)
at com.oracle.javafx.scenebuilder.kit.editor.panel.content.WorkspaceController.sceneDidChange(WorkspaceController.java:104)
at com.oracle.javafx.scenebuilder.kit.editor.panel.content.WorkspaceController.access$000(WorkspaceController.java:28)
at com.oracle.javafx.scenebuilder.kit.editor.panel.content.WorkspaceController$1.changed(WorkspaceController.java:59)
at com.oracle.javafx.scenebuilder.kit.editor.panel.content.WorkspaceController$1.changed(WorkspaceController.java:56)
at com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(ExpressionHelper.java:176)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ReadOnlyObjectWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyObjectWrapper.java:176)
at javafx.beans.property.ReadOnlyObjectWrapper.fireValueChangedEvent(ReadOnlyObjectWrapper.java:142)
at javafx.scene.Node$ReadOnlyObjectWrapperManualFire.fireSuperValueChangedEvent(Node.java:774)
at javafx.scene.Node.invalidatedScenes(Node.java:823)
at javafx.scene.Node.setScenes(Node.java:832)
at javafx.scene.Scene$9.invalidated(Scene.java:1093)
at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:111)
at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:145)
at javafx.scene.Scene.setRoot(Scene.java:1042)
at javafx.scene.Scene.<init>(Scene.java:361)
at javafx.scene.Scene.<init>(Scene.java:220)
at com.oracle.javafx.scenebuilder.probe.HostWindowController.openWindow(HostWindowController.java:43)
at com.oracle.javafx.scenebuilder.probe.MainWindowController.onShowContentViewAction(MainWindowController.java:355)
... 53 more