NullReferenceException: Object reference not set to an instance of an object PlayerControl.Update () (at Assets/PlayerControl.cs:20) <-lineno:-

using UnityEngine; using System.Collections;

public class PlayerControl : MonoBehaviour { [HideInInspector] public bool facingRight = true; // For determining which way the player is currently facing. [HideInInspector] public bool jump = false; // Condition for whether the player should jump.

 public float moveForce = 365f;            // Amount of force added to move the player left and right.
 public float maxSpeed = 5f;                // The fastest the player can travel in the x axis.
         
 public float jumpForce = 1000f;            // Amount of force added when the player jumps.

 private Transform groundCheck;            // A position marking where to check if the player is grounded.
 private bool grounded = false;            // Whether or not the player is grounded.


 void Awake()
 {
     // Setting up references.
     groundCheck = transform.Find("groundCheck");

 }

 void Update()
 {
     // The player is grounded if a linecast to the groundcheck position hits anything on the ground layer.
     grounded = Physics2D.Linecast(transform.position, groundCheck.position, 1 << LayerMask.NameToLayer("Ground"));  

     // If the jump button is pressed and the player is grounded then the player should jump.
     if(Input.GetButtonDown("Jump") && grounded)
         jump = true;
 }


 void FixedUpdate ()
 {
     // Cache the horizontal input.
     float h = Input.GetAxis("Horizontal");

     // If the player is changing direction (h has a different sign to velocity.x) or hasn't reached maxSpeed yet...
     if(h * GetComponent<Rigidbody2D>().velocity.x < maxSpeed)
         // ... add a force to the player.
         GetComponent<Rigidbody2D>().AddForce(Vector2.right * h * moveForce);

     // If the player's horizontal velocity is greater than the maxSpeed...
     if(Mathf.Abs(GetComponent<Rigidbody2D>().velocity.x) > maxSpeed)
         // ... set the player's velocity to the maxSpeed in the x axis.
         GetComponent<Rigidbody2D>().velocity = new Vector2(Mathf.Sign(GetComponent<Rigidbody2D>().velocity.x) * maxSpeed, GetComponent<Rigidbody2D>().velocity.y);

     // If the input is moving the player right and the player is facing left...
     if(h > 0 && !facingRight)
         // ... flip the player.
         Flip();
     // Otherwise if the input is moving the player left and the player is facing right...
     else if(h < 0 && facingRight)
         // ... flip the player.
         Flip();

     // If the player should jump...
     if(jump)
     {
         // Add a vertical force to the player.
         GetComponent<Rigidbody2D>().AddForce(new Vector2(0f, jumpForce));

         // Make sure the player can't jump again until the jump conditions from Update are satisfied.
         jump = false;
     }
 }


 void Flip ()
 {
     // Switch the way the player is labelled as facing.
     facingRight = !facingRight;

     // Multiply the player's x local scale by -1.
     Vector3 theScale = transform.localScale;
     theScale.x *= -1;
     transform.localScale = theScale;
 }