ADDITIONAL SYSTEM INFORMATION :
Windows 10/Red Hat
Java 9 and 10

A DESCRIPTION OF THE PROBLEM :
Seems to be a duplicate of https://bugs.openjdk.java.net/browse/JDK-8095034 that should have been fixed in latest release of Java 8.

Stack Trace:
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at javafx.scene.Scene$ScenePulseListener.synchronizeSceneNodes(Unknown Source)
at javafx.scene.Scene$ScenePulseListener.pulse(Unknown Source)
at com.sun.javafx.tk.Toolkit.lambda$runPulse$3(Unknown Source)
at java.security.AccessController.doPrivileged(Unknown Source)
at com.sun.javafx.tk.Toolkit.runPulse(Unknown Source)
at com.sun.javafx.tk.Toolkit.firePulse(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulseFromQueue(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runTool (Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
at com.sun.glass.ui.GtkApplication._runLoop(Unknown Source)
at java.lang.Thread.run(Thread.java:744)


FREQUENCY : often