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);
			};
		}
	}
}

Null Reference Exceptions happen when you try to access someObject.someMember when someObject doesn’t have anything assigned to it. The only thing on line 86 that can be null is highscoretext, so you probably don’t have a Text component on the object for GetComponent to retrieve in your Start function.