Object Reference Not Set to an Instance of an Object

I'm trying to add a high score to display in my game. I always get the error: NullReferenceException: Object reference not set to an instance of an object PlayerController.Update () (at Assets/Scripts/PlayerController.cs:86) I can't find what I'm doing wrong. Here is the rest of my code:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.SceneManagement;
 using UnityEngine.UI;
 
 public class PlayerController : MonoBehaviour {
     public Rigidbody2D rb;
     public float jetpackForce = 75.0f;
     public float forwardMovementSpeed = 3.0f;
     private bool dead = false;
     private int coins = 0;
     public Texture2D coinIconTexture;
     public int HighScore;
     public Text highscoretext; 
 
     // Use this for initialization
     void Start () 
     {
         GetComponent<Rigidbody2D>();
         highscoretext = GetComponent <Text> ();
     }
 
     // Update is called once per frame
 
     void FixedUpdate () 
     {
         bool jetpackActive = Input.GetButton("Fire1");
 
         jetpackActive = jetpackActive && !dead;
 
         if (jetpackActive)
         {
             GetComponent<Rigidbody2D>().AddForce(new Vector2(0, jetpackForce));
         }
 
         if (!dead)
         {
             Vector2 newVelocity = GetComponent<Rigidbody2D>().velocity;
             newVelocity.x = forwardMovementSpeed;
             GetComponent<Rigidbody2D>().velocity = newVelocity;
         }
     } 
     void CollectCoin(Collider2D coinCollider)
     {
         coins++;
 
         Destroy(coinCollider.gameObject);
 
     }
 
 
     void OnTriggerEnter2D(Collider2D collider)
     {
         if (collider.gameObject.CompareTag("Coins"))
             CollectCoin(collider);
         else
             HitByLaser(collider);
     }
 
     void HitByLaser(Collider2D laserCollider)
     {
         dead = true;
     }
 
     void DisplayCoinsCount()
     {
         Rect coinIconRect = new Rect(10, 10, 32, 32);
         GUI.DrawTexture(coinIconRect, coinIconTexture);                         
 
         GUIStyle style = new GUIStyle();
         style.fontSize = 39;
         style.fontStyle = FontStyle.Bold;
         style.normal.textColor = Color.red;
 
         Rect labelRect = new Rect(coinIconRect.xMax, coinIconRect.y, 60, 32);
         GUI.Label(labelRect, coins.ToString(), style);
     }
 
     void Update()
     {
 
         if (dead)
             HighScore = coins;
         PlayerPrefs.SetInt ("High Score", HighScore);
         {
             highscoretext.text = "High Score is " + HighScore;
         }
     }
 
 
     void OnGUI()
     {
         DisplayCoinsCount();
 
         DisplayRestartButton();
     }
 
     void DisplayRestartButton()
     {
         if (dead)
         {
             Rect buttonRect = new Rect(Screen.width * 0.35f, Screen.height * 0.45f, Screen.width * 0.30f, Screen.height * 0.1f);
             if (GUI.Button(buttonRect, "Tap to restart!"))
             {
                 UnityEngine.SceneManagement.SceneManager.LoadScene(UnityEngine.SceneManagement.SceneManager.GetActiveScene().buildIndex);
             };
         }
     }
 }