code: private FXMLLoader loadSynchronously(final URL resource, final Optional<ResourceBundle> bundle) throws IllegalStateException {
  
  		final FXMLLoader loader = new FXMLLoader(resource, bundle.orElse(null));
  		loader.setControllerFactory(this::createControllerForType);
  
  		try {
  			loader.load();
  		} catch (final IOException | IllegalStateException e) {
  			throw new IllegalStateException("Cannot load " + getConventionalName(), e);
  		}
  
  		return loader;
  	}
docs: Load synchronously.
  
  @param resource
  the resource
  @param bundle
  the bundle
  @return the FXML loader
  @throws IllegalStateException
  the illegal state exception