The following testcase throws NPE:

    at com.sun.javafx.tk.quantum.EmbeddedPainter.run(EmbeddedPainter.java:112)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)
    at com.sun.prism.render.RenderJob.run(RenderJob.java:56)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:131)
    at java.lang.Thread.run(Thread.java:722)

<code>

public class Test {
    
    public static void main(String[] args) {
        JFrame frame = new JFrame("test");
        
        final JFXPanel fxPanel = new JFXPanel();

        Platform.runLater(new Runnable() {
            @Override
            public void run() {
                Region rgn = new Region();
                Scene scene = new Scene(rgn);
                rgn.setStyle("-fx-background-color: #00ff00;");
                fxPanel.setScene(scene);
            }
        });

        frame.getContentPane().setBackground(java.awt.Color.RED);
        frame.getContentPane().setPreferredSize(new Dimension(400, 300));
        frame.pack();

        fxPanel.setSize(400, 300);

        frame.getContentPane().add(fxPanel);
        frame.getContentPane().remove(fxPanel);
        frame.getContentPane().add(fxPanel);
        frame.setVisible(true);
    }
}

</code>