Trying to rewrite the Hangman code now that i am done with the course, but i am getting an error.

Exception in thread "main" java.lang.NullPointerException
    at com.company.Prompter.inputGuess(Prompter.java:30)
    at com.company.Main.main(Main.java:10)

package com.company;


public class Main {

    public static void main(String[] args) {

        Game game = new Game("treehouse");
        Prompter prompter = new Prompter();
        prompter.inputGuess();
    }

}

package com.company;

import java.util.Scanner;

/**
 * Created by edmon on 1/30/2017.
 */

public class Prompter {
    public static Scanner scanner = new Scanner(System.in);
    private String name;
    private Game game;

    public Prompter(){

    }

    public String getName(){
        return this.name;
    }

    public void inputGuess(){
        System.out.println("what is your name? ");
        this.name = scanner.nextLine();
        System.out.printf("%s, what is the word? \n", name);
        System.out.println("Please enter a letter to guess. ");
        String guess = scanner.nextLine();
        game.applyGuess(guess);
        System.out.printf("This is your progress so far: ",game.progress());

    }
}

package com.company;

/**
 * Created by edmon on 1/30/2017.
 */
public class Game {
    private String answer;
    private String hits;
    private String misses;
    private Prompter prompter;

    public Game(String answer){
        this.answer = answer.toLowerCase();
        hits = "";
        misses = "";
    }

    public void applyGuess(String letter){
        if(letter.length() == 0){
            throw new IllegalArgumentException( prompter.getName() + " nothing was entered.");
        }else{
            applyGuess(letter.charAt(0));
        }


    }

    public char normalize(char letter){
        if(!Character.isLetter(letter)){
            throw new IllegalArgumentException( prompter.getName() + " please enter a letter.");
        }else{
            letter = Character.toLowerCase(letter);
            return letter;
        }
    }

    public void applyGuess(char letter){
        letter = normalize(letter);
        if(answer.indexOf(letter) != -1){
            hits += letter;
        }else{
            misses += letter;
        }
    }

    public String progress(){
        String progress = "";
        for(char letters: answer.toCharArray()){
            String display = "-";
            if(hits.indexOf(letters) != -1){
                display += letters;
            }
            progress += display;
        }
        return progress;
    }
}