JavaFX Image класс, возвращающий исключение нулевой точки

Question

Занятие, чтобы узнать больше о Java и JavaFX. Не совсем уверен, что я делаю здесь не так. Я получаю исключение нулевого указателя при попытке запустить приложение.

    import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.FlowPane;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class CreditCardInput extends Application {
    TextField creditCardNo;
    TextField expDate;
    Image creditCardImage;
    TextField ccvInput;
    String imageOutput;
    ImageView imageView;

    public CreditCardInput() {

        this.creditCardNo = new TextField("xxxxxxxxxxxxxxxx");
        this.expDate = new TextField("MM/YYYY");
        this.ccvInput = new TextField("xxx");
    }

    public StackPane drawForm(){
        StackPane layout = new StackPane();

        for(int col=0;col<2;col++){
            for(int row=0; row<4;row++){

            }
        }
        return layout;
    }
    public String creditCardNumberValidate(){
        Scanner ccnInput = new Scanner(System.in);

        String ccInput =  this.ccvInput.getText();

        char[] intArray = ccInput.toCharArray();
        StringBuilder doubleDigitCheck = new StringBuilder(intArray[0]+intArray[1]);
        System.out.println(ccInput);

        String str = new String(doubleDigitCheck);
        boolean bMatches = str.matches("^[34]$");

        int checkValue = Integer.parseInt(String.valueOf(intArray[0]));

        String ccvOutput;

        switch(checkValue){
            case 3:
                if(str.matches("^{34}$")){
                    return "amex.png";
                }
                if(str.matches("^[37]$")){
                    return "amex.png";
                }
                if(str.matches("^[35]$")){
                    return "jcb.png";
                }

            case 4:
                ccvOutput = "visa.png";
            case 5:
                ccvOutput = "mastercard.png";
            default:
                ccvOutput = "invalid";
        }
        this.imageOutput = ccvOutput;
        return this.imageOutput;
    }



    public ImageView cerditCardImage()  {

        try {
            this.creditCardImage = new Image(new FileInputStream(imageOutput));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        this.imageView = new ImageView(this.creditCardImage);

        return this.imageView;
    }
    @Override
    public void start(Stage primaryStage){
        primaryStage.setTitle("Credit Card Number");
        Group root = new Group(this.imageView, drawForm());
        FlowPane layout = new FlowPane();
        Scene scene = new Scene(root,300,300);
        Label cardNoTitle = new Label("Card Number");
        Label expDateLabel = new Label("Exp Date");
        Label cvvLabel = new Label("CVV");

        layout.getChildren();
        layout.getChildren().addAll(creditCardNo,expDateLabel,expDate,cvvLabel,ccvInput);

        root.getChildren().add(layout);

        primaryStage.setScene(scene);
        primaryStage.show();

    }



    public static void main(String[] args){
        launch(args);
        System.out.println("Launched!");
    }
}

Сообщение об ошибке, которое я получаю:

/Applications/IntelliJ IDEA CE.app/Contents/jbr/Contents/Home/bin/java" "-javaagent:/Applications/IntelliJ IDEA CE.app/Contents/lib/idea_rt.jar=61275:/Applications/IntelliJ IDEA CE.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath "/Volumes/external disk/dropbox/Dropbox/UCLA_School/Java2/CreditCardInput/out/production/CreditCardInput" CreditCardInput
Exception in Application start method
java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:473)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:372)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1051)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:973)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:198)
    at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.NullPointerException: Children: child node is null: parent = Group@415d8a95
    at javafx.graphics/javafx.scene.Parent$3.onProposedChange(Parent.java:546)
    at javafx.base/com.sun.javafx.collections.VetoableListDecorator.addAll(VetoableListDecorator.java:234)
    at javafx.base/com.sun.javafx.collections.VetoableListDecorator.addAll(VetoableListDecorator.java:103)
    at javafx.graphics/javafx.scene.Group.<init>(Group.java:106)
    at CreditCardInput.start(CreditCardInput.java:96)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:919)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$11(PlatformImpl.java:449)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$9(PlatformImpl.java:418)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:417)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
Exception running application CreditCardInput

Process finished with exit code 1

Любая помощь с благодарностью.