Weird error for treestory.

package com.teamtreehouse;

import java.io.IOException;
import java.util.Arrays;
import java.util.List;

public class Main {

    public static void main(String[] args) {

        Prompter prompter = new Prompter();
        String story = null;
        try {
            prompter.promptForStory();
        } catch (IOException ioe){
            ioe.printStackTrace();
        }


        Template tmpl = new Template(story);




        prompter.run(tmpl);


    }
}

package com.teamtreehouse;

import java.io.*;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;


public class Prompter {
    private BufferedReader mReader;
    private Set<String> mCensoredWords;

    public Prompter() {
        mReader = new BufferedReader(new InputStreamReader(System.in));
        loadCensoredWords();
    }

    private void loadCensoredWords() {
        mCensoredWords = new HashSet<String>();
        Path file = Paths.get("resources", "censored_words.txt");
        List<String> words = null;
        try {
            words = Files.readAllLines(file);
        } catch (IOException e) {
            System.out.println("Couldn't load censored words");
            e.printStackTrace();
        }
        mCensoredWords.addAll(words);
    }

    public void run(Template tmpl) {
        List<String> results = null;
        try {
            results = promptForWords(tmpl);
        } catch (IOException e) {
            System.out.println("There was a problem prompting for words");
            e.printStackTrace();
            System.exit(0);
        }

        String yourStory = tmpl.render(results);
        System.out.printf("Your TreeStory:%n%n%s", yourStory);
    }

    public List<String> promptForWords(Template tmpl) throws IOException {
        List<String> words = new ArrayList<String>();
        for (String phrase : tmpl.getPlaceHolders()) {
            String word = promptForWord(phrase);
            words.add(word);
        }
        return words;
    }



    public String promptForWord(String phrase) throws IOException {
        String response = null;

        do {
            System.out.printf("Enter the response for %s: ", phrase);
            response = mReader.readLine();
            if (mCensoredWords.contains(response)){
                System.out.printf("Sorry, %s is not allowed.%n", response);
            }
        }while (mCensoredWords.contains(response));

        return response;
    }

    public String promptForStory () throws IOException{
        String newStory = null;

        System.out.println("Create your story with __word__ for blank spaces");
        newStory = mReader.readLine();

        return newStory;
    }
}