having problem in solving NullPointerExecption error

public class Hangman{
    public static void main(String[] args){
        Game game = new Game("testing");
        Prompter prompter = new Prompter(game);
        prompter.displayProgress();
        boolean isHit = prompter.promptForGuess();
        if(isHit){
        System.out.println("You got a hit");
        }else{
        System.out.println("You missed it");
        }
        prompter.displayProgress();
    }
}

import java.io.Console;
public class Prompter{

    private Game mGame;

    public Prompter(Game game){
    mGame = game;
    }

    public boolean promptForGuess(){
    Console console = System.console();
    String guessAsString = console.readLine("Enter a letter: ");
    char guess = guessAsString.charAt(0);
    return mGame.applyGuess(guess);
    }

    public void displayProgress(){
    System.out.printf("Try to solve: %s\n", mGame.getCurrentProgress());
    }


}

public class Game{
    private String mAnswer;
    private String mHit;
    private String mMisses;

    public Game (String answer){
        mAnswer = answer;
    }

    public boolean applyGuess(char letter){
        boolean isHit = mAnswer.indexOf(letter) >= 0;
        //if indexOf value is -1 meaning the char is not existed in the string.
        if(isHit){
        mHit += letter;
        }else{
        mMisses += letter;
        }
        return isHit;
    }

    public String getCurrentProgress(){
    String progress = "";
     for(char letter : mAnswer.toCharArray()){
        char display = '-';
        if (mHit.indexOf(letter) >= 0){
        display = letter;
        }//if
        progress += display;
     }//for
     return progress;
    }//getCurrentProgress method




}