Why doesnt this Java code, provided by oracle, throw an exception when run?

Question

I have some sample code, which shows how to display html in java, throws the following exceptions when i run the main method:

java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$152(LauncherImpl.java:182)
    at com.sun.javafx.application.LauncherImpl$$Lambda$7/4781857.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ExceptionInInitializerError
    at WebViewSample.start(WebViewSample.java:44)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$159(LauncherImpl.java:863)
    at com.sun.javafx.application.LauncherImpl$$Lambda$57/32558093.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$172(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl$$Lambda$52/5240121.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null$170(PlatformImpl.java:295)
    at com.sun.javafx.application.PlatformImpl$$Lambda$55/20053859.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$171(PlatformImpl.java:294)
    at com.sun.javafx.application.PlatformImpl$$Lambda$54/20131899.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
    at com.sun.glass.ui.win.WinApplication$$Lambda$43/11473758.run(Unknown Source)
    ... 1 more
Caused by: java.lang.NullPointerException
at Browser.<clinit>(WebViewSample.java:78)

Why is this exception being thrown and how do I diagnose and fix this problem?

Java Sample Code Provided by Oracle:

import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.ListChangeListener;
import javafx.collections.ListChangeListener.Change;
import javafx.concurrent.Worker.State;
import javafx.event.ActionEvent;
import javafx.event.Event;
import javafx.event.EventHandler;
import javafx.geometry.HPos;
import javafx.geometry.Pos;
import javafx.geometry.VPos;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.control.Hyperlink;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.Region;
import javafx.scene.paint.Color;
import javafx.scene.web.PopupFeatures;
import javafx.scene.web.WebEngine;
import javafx.scene.web.WebHistory;
import javafx.scene.web.WebHistory.Entry;
import javafx.scene.web.WebView;
import javafx.stage.Stage;
import javafx.util.Callback;
import netscape.javascript.JSObject;
import java.net.*;


public class WebViewSample extends Application {

    private Scene scene;

    @Override
    public void start(Stage stage) {
        // create scene
        stage.setTitle("Web View");
        scene = new Scene(new Browser(), 750, 500, Color.web("#666970"));
        stage.setScene(scene);
        // apply CSS style
        scene.getStylesheets().add("webviewsample/BrowserToolbar.css");
        // show stage
        stage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}
class Browser extends Region {

    private HBox toolBar;
    private static String[] imageFiles = new String[]{
        "product.png",
        "blog.png",
        "documentation.png",
        "partners.png",
        "help.png"
    };
    private static String[] captions = new String[]{
        "Products",
        "Blogs",
        "Documentation",
        "Partners",
        "Help"
    };
    private static String[] urls = new String[]{
        "http://www.oracle.com/products/index.html",
        "http://blogs.oracle.com/",
        "http://docs.oracle.com/javase/index.html",
        "http://www.oracle.com/partners/index.html",
        WebViewSample.class.getResource("help.html").toExternalForm()
    };
    final ImageView selectedImage = new ImageView();
    final Hyperlink[] hpls = new Hyperlink[captions.length];
    final Image[] images = new Image[imageFiles.length];
    final WebView browser = new jxWebView();
    final WebEngine webEngine = browser.getEngine();
    final Button showPrevDoc = new Button("Toggle Previous Docs");
    final WebView smallView = new WebView();
    final ComboBox comboBox = new ComboBox();
    private boolean needDocumentationButton = false;

    public Browser() {
        //apply the styles
        getStyleClass().add("browser");

        for (int i = 0; i < captions.length; i++) {
            // create hyperlinks
            Hyperlink hpl = hpls[i] = new Hyperlink(captions[i]);
            Image image = images[i] =
                    new Image(getClass().getResourceAsStream(imageFiles[i]));
            hpl.setGraphic(new ImageView(image));
            final String url = urls[i];
            final boolean addButton = (hpl.getText().equals("Documentation"));

            // process event 
            hpl.setOnAction(new EventHandler<ActionEvent>() {
                @Override
                public void handle(ActionEvent e) {
                    needDocumentationButton = addButton;
                    webEngine.load(url);
                }
            });
        }

        comboBox.setPrefWidth(60);

        // create the toolbar
        toolBar = new HBox();
        toolBar.setAlignment(Pos.CENTER);
        toolBar.getStyleClass().add("browser-toolbar");
        toolBar.getChildren().add(comboBox);
        toolBar.getChildren().addAll(hpls);
        toolBar.getChildren().add(createSpacer());

        //set action for the button
        showPrevDoc.setOnAction(new EventHandler() {
            @Override
            public void handle(Event t) {
                webEngine.executeScript("toggleDisplay('PrevRel')");
            }           
        });

        smallView.setPrefSize(120, 80);

        //handle popup windows
        webEngine.setCreatePopupHandler(
            new Callback<PopupFeatures, WebEngine>() {
                @Override public WebEngine call(PopupFeatures config) {
                    smallView.setFontScale(0.8);
                    if (!toolBar.getChildren().contains(smallView)) {
                        toolBar.getChildren().add(smallView);
                    }
                    return smallView.getEngine();
                }
             }
        );

        //process history
        final WebHistory history = webEngine.getHistory();
        history.getEntries().addListener(new 
            ListChangeListener<WebHistory.Entry>(){
                @Override
                public void onChanged(Change<? extends Entry> c) {
                    c.next();
                    for (Entry e : c.getRemoved()) {
                        comboBox.getItems().remove(e.getUrl());
                    }
                    for (Entry e : c.getAddedSubList()) {
                        comboBox.getItems().add(e.getUrl());
                    }
                }
        });

        //set the behavior for the history combobox               
        comboBox.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent ev) {
                int offset =
                        comboBox.getSelectionModel().getSelectedIndex()
                        - history.getCurrentIndex();
                history.go(offset);
            }
        });


        // process page loading
        webEngine.getLoadWorker().stateProperty().addListener(
            new ChangeListener<State>() {
                @Override
                public void changed(ObservableValue<? extends State> ov,
                    State oldState, State newState) {
                    toolBar.getChildren().remove(showPrevDoc);    
                    if (newState == State.SUCCEEDED) {
                            JSObject win = 
                                (JSObject) webEngine.executeScript("window");
                            win.setMember("app", new JavaApp());
                            if (needDocumentationButton) {
                                toolBar.getChildren().add(showPrevDoc);
                            }
                        }
                    }
                }
        );

        // load the home page        
        webEngine.load("http://www.oracle.com/products/index.html");

        //add components
        getChildren().add(toolBar);
        getChildren().add(browser);
    }

    // JavaScript interface object
    public class JavaApp {

        public void exit() {
            Platform.exit();
        }
    }

    private Node createSpacer() {
        Region spacer = new Region();
        HBox.setHgrow(spacer, Priority.ALWAYS);
        return spacer;
    }

    @Override
    protected void layoutChildren() {
        double w = getWidth();
        double h = getHeight();
        double tbHeight = toolBar.prefHeight(w);
        layoutInArea(browser,0,0,w,h-tbHeight,0,HPos.CENTER,VPos.CENTER);
        layoutInArea(toolBar,0,h-tbHeight,w,tbHeight,0,HPos.CENTER,VPos.CENTER);
    }

    @Override
    protected double computePrefWidth(double height) {
        return 750;
    }

    @Override
    protected double computePrefHeight(double width) {
        return 600;
    }
}

NOTE: I am awar eof what a null pointer exception is, i just have no clue why it is being thrown here and how launcg(args) in the main method is related