A jvm crash occurs if you load a document in a locationProperty listener.

    webView.getEngine().locationProperty().addListener(new ChangeListener<String>() {
      @Override public void changed(ObservableValue<? extends String> prop, final String before, String after) {
        if (!"http://www.google.com".equals(after)) {
          webView.getEngine().load("http://www.google.com");
        }
      }
    });

Crash log and sample app attached.