// This is executed:
                SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new JFXPanel(); //Somehow prepares the JavaFX toolkit

                                // Other stuff is done here

                                Platform.runLater(new Runnable() {
                           public void run() {
                              test(); // The code below
                           }
                        });
            }
        });

/////////////////////////////////////////////////////

       void test() {

                JFXPanel jfx = new JFXPanel();

        final JFrame dialog = new JFrame();
        dialog.setTitle("I'm a dialog");
        BorderPane root = new BorderPane();
        dialog.setSize(880, 550);
        dialog.setResizable(false);
        Scene ds = new Scene(root);
        jfx.setScene(ds);
        dialog.add(jfx);
        dialog.setVisible(true);

        WebView browser = new WebView();
        browser.setDisable(true);
        WebEngine webEngine = browser.getEngine();
        webEngine.load("http://www.example.com"); //When commenting this line out, the crash does not occur.

        root.setCenter(browser);
        }