Null Pointer Exception error

Exception in thread "main" java.lang.NullPointerException
    at Prompter.promptForGuess(Prompter.java:17)
    at Hangman.main(Hangman.java:9)

public class Hangman {
  public static void main(String[] args) {
    Game game = new Game("treehouse");
    Prompter prompter = new Prompter (game);
    boolean isHit = prompter.promptForGuess();
    if (isHit) {
      System.out.println("We got a hit!!");
    } else {
      System.out.println("Whoops! that was a miss!");
    }
  }
}

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(null, "Enter a letter: ");
    char guess = guessAsString.charAt(0);
    return mGame.applyGuess(guess);
  }
}

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

  public Game(String answer) {
    mAnswer = answer;
    mHits = "";
    mMisses = "";
  }

  public boolean applyGuess (char letter) {
    boolean isHit = mAnswer.indexOf(letter) >= 0;
    if (isHit) {
      mHits += letter;
    } else {
      mMisses += letter;
    }

    return isHit;
  }
}