NullReferenceException: Object reference not set to an instance of an object

Okay I'm having this problem, and I'm not sure how to fix it!

I'm following this tutorial to make a visual novel. I'm a complete beginner! http://www.indiana.edu/~gamedev/2015/09/27/creating-a-visual-novel-in-unity/

I'm struggling with the part where I've just made my Character prefab (it contains my static character and all their poses), but they won't appear in the scene. I've even tried dragging the prefab into the scene directly. It even won't appear in the gameplay box. The layer orders are correct, and I'm assuming the reason they're not showing up must have to do with the error message I have:

 NullReferenceException: Object reference not set to an instance of an object
 DialogueManager.Start () (at Assets/Scripts/DialogueManager.cs:29)

And these are the codes I'm working with:

Dialogue Parser:

using UnityEngine; using System.Collections; using UnityEditor; using System.Text; using System.IO; using System.Text.RegularExpressions; using System.Collections.Generic;

public class DialogueParser : MonoBehaviour {

 struct DialogueLine {
     public string name;
     public string content;
     public int pose;
     public string position;
     public string[] options;

     public DialogueLine(string Name, string Content, int Pose, string Position) {
         name = Name;
         content = Content;
         pose = Pose;
         position = Position;
         options = new string[0];
     }
 }

 List<DialogueLine> lines;

 // Use this for initialization
 void Start () {
     string file = "Assets/Data/Dialogue";
     string sceneNum = EditorApplication.currentScene;
     sceneNum = Regex.Replace (sceneNum, "[^0-9]", "");
     file += sceneNum;
     file += ".txt";

     lines = new List<DialogueLine>();

     LoadDialogue (file);
 }

 // Update is called once per frame
 void Update () {

 }

 void LoadDialogue(string filename) {
     string line;
     StreamReader r = new StreamReader (filename);

     using (r) {
         do {
             line = r.ReadLine();
             if (line != null) {
                 string[] lineData = line.Split(';');
                 if (lineData[0] == "Player") {
                     DialogueLine lineEntry = new DialogueLine(lineData[0], "", 0, "");
                     lineEntry.options = new string[lineData.Length-1];
                     for (int i = 1; i < lineData.Length; i++) {
                         lineEntry.options[i-1] = lineData[i];
                     }
                     lines.Add(lineEntry);
                 } else {
                     DialogueLine lineEntry = new DialogueLine(lineData[0], lineData[1], int.Parse(lineData[2]), lineData[3]);
                     lines.Add(lineEntry);
                 }
             }
         }
         while (line != null);
         r.Close();
     }
 }

 public string GetPosition(int lineNumber) {
     if (lineNumber < lines.Count) {
         return lines[lineNumber].position;
     }
     return "";
 }

 public string GetName(int lineNumber) {
     if (lineNumber < lines.Count) {
         return lines[lineNumber].name;
     }
     return "";
 }

 public string GetContent(int lineNumber) {
     if (lineNumber < lines.Count) {
         return lines[lineNumber].content;
     }
     return "";
 }

 public int GetPose(int lineNumber) {
     if (lineNumber < lines.Count) {
         return lines[lineNumber].pose;
     }
     return 0;
 }

 public string[] GetOptions(int lineNumber) {
     if (lineNumber < lines.Count) {
         return lines[lineNumber].options;
     }
     return new string[0];
 }

}

Dialogue Manager:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 using System.Collections.Generic;
 
 public class DialogueManager : MonoBehaviour {
 
     DialogueParser parser;
 
     public string dialogue, characterName;
     public int lineNum;
     int pose;
     string position;
     string[] options;
     public bool playerTalking;
     List<Button> buttons = new List<Button> ();
 
     public Text dialogueBox;
     public Text nameBox;
     public GameObject choiceBox;
 
     // Use this for initialization
     void Start () {
         dialogue = "";
         characterName = "";
         pose = 0;
         position = "L";
         playerTalking = false;
         parser = GameObject.Find("DialogueParser").GetComponent<DialogueParser>();
         lineNum = 0;
     }
 
     // Update is called once per frame
     void Update () {
         if (Input.GetMouseButtonDown (0) && playerTalking == false) {
             ShowDialogue();
 
             lineNum++;
         }
 
         UpdateUI ();
     }
 
     public void ShowDialogue() {
         ResetImages ();
         ParseLine ();
     }
 
     void UpdateUI() {
         if (!playerTalking) {
             ClearButtons();
         }
         dialogueBox.text = dialogue;
         nameBox.text = characterName;
     }
 
     void ClearButtons() {
         for (int i = 0; i < buttons.Count; i++) {
             print ("Clearing buttons");
             Button b = buttons[i];
             buttons.Remove(b);
             Destroy(b.gameObject);
         }
     }
 
     void ParseLine() {
         if (parser.GetName (lineNum) != "Player") {
             playerTalking = false;
             characterName = parser.GetName (lineNum);
             dialogue = parser.GetContent (lineNum);
             pose = parser.GetPose (lineNum);
             position = parser.GetPosition (lineNum);
             DisplayImages();
         } else {
             playerTalking = true;
             characterName = "";
             dialogue = "";
             pose = 0;
             position = "";
             options = parser.GetOptions(lineNum);
             CreateButtons();
         }
     }
 
     void CreateButtons() {
         for (int i = 0; i < options.Length; i++) {
             GameObject button = (GameObject)Instantiate(choiceBox);
             Button b = button.GetComponent<Button>();
             ChoiceButton cb = button.GetComponent<ChoiceButton>();
             cb.SetText(options[i].Split(':')[0]);
             cb.option = options[i].Split(':')[1];
             cb.box = this;
             b.transform.SetParent(this.transform);
             b.transform.localPosition = new Vector3(0,-25 + (i*50));
             b.transform.localScale = new Vector3(1, 1, 1);
             buttons.Add (b);
         }
     }
 
     void ResetImages() {
         if (characterName != "") {
             GameObject character = GameObject.Find (characterName);
             SpriteRenderer currSprite = character.GetComponent<SpriteRenderer>();
             currSprite.sprite = null;
         }
     }
 
     void DisplayImages() {
         if (characterName != "") {
             GameObject character = GameObject.Find(characterName);
 
             SetSpritePositions(character);
 
             SpriteRenderer currSprite = character.GetComponent<SpriteRenderer>();
             currSprite.sprite = character.GetComponent<Character>().characterPoses[pose];
         }
     }
 
 
     void SetSpritePositions(GameObject spriteObj) {
         if (position == "L") {
             spriteObj.transform.position = new Vector3 (-6, 0);
         } else if (position == "R") {
             spriteObj.transform.position = new Vector3 (6, 0);
         }
         spriteObj.transform.position = new Vector3 (spriteObj.transform.position.x, spriteObj.transform.position.y, 0);
     }
 }

I hope this is enough information to work with, but I can post anything else that's needed! Please let me know if anyone knows how I can fix this problem. :)

I'm sure it must be a simple fix, but I'm so new to all of this...I'm very overwhelmed by everything @_@

Thank you!