How to fix this Unity error?

Question

I am following a make a game course and I keep getting an error in m code, and I have no clue how to fix it. Here is the problem code:

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

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

I am getting the error "Null Reference Exception: Object reference not set to an instance of an object". What do I need to do to fix it?

Here is all of my code:

using System; using UnityEngine;

namespace UnityStandardAssets._2D { public class PlatformerCharacter2D : MonoBehaviour { [SerializeField] private float m_MaxSpeed = 10f; // The fastest the player can travel in the x axis. [SerializeField] private float m_JumpForce = 400f; // Amount of force added when the player jumps. [Range(0, 1)] [SerializeField] private float m_CrouchSpeed = .36f; // Amount of maxSpeed applied to crouching movement. 1 = 100% [SerializeField] private bool m_AirControl = false; // Whether or not a player can steer while jumping; [SerializeField] private LayerMask m_WhatIsGround; // A mask determining what is ground to the character

    private Transform m_GroundCheck;    // A position marking where to check if the player is grounded.
    const float k_GroundedRadius = .2f; // Radius of the overlap circle to determine if grounded
    private bool m_Grounded;            // Whether or not the player is grounded.
    private Transform m_CeilingCheck;   // A position marking where to check for ceilings
    const float k_CeilingRadius = .01f; // Radius of the overlap circle to determine if the player can stand up
    private Animator m_Anim;            // Reference to the player's animator component.
    private Rigidbody2D m_Rigidbody2D;
    private bool m_FacingRight = true;  // For determining which way the player is currently facing.

    Transform playerGraphics;           // Be a reference to the graphics so we can change direction

    public object PlayerCharacter2d { get; private set; }

    private void Awake()
    {
        // Setting up references.
        m_GroundCheck = transform.Find("GroundCheck");
        m_CeilingCheck = transform.Find("CeilingCheck");
        m_Anim = GetComponent<Animator>();
        m_Rigidbody2D = GetComponent<Rigidbody2D>();
        playerGraphics = transform.FindChild("Graphics");
        if (playerGraphics = null)
        {
            Debug.LogError("Let's freak out! There is no 'Graphics' object as a child of the player");
                } 
    }


    private void FixedUpdate()
    {
        m_Grounded = false;

        // The player is grounded if a circlecast to the groundcheck position hits anything designated as ground
        // This can be done using layers instead but Sample Assets will not overwrite your project settings.
        Collider2D[] colliders = Physics2D.OverlapCircleAll(m_GroundCheck.position, k_GroundedRadius, m_WhatIsGround);
        for (int i = 0; i < colliders.Length; i++)
        {
            if (colliders[i].gameObject != gameObject)
                m_Grounded = true;
        }
        m_Anim.SetBool("Ground", m_Grounded);

        // Set the vertical animation
        m_Anim.SetFloat("vSpeed", m_Rigidbody2D.velocity.y);
    }


    public void Move(float move, bool crouch, bool jump)
    {
        // If crouching, check to see if the character can stand up
        if (!crouch && m_Anim.GetBool("Crouch"))
        {
            // If the character has a ceiling preventing them from standing up, keep them crouching
            if (Physics2D.OverlapCircle(m_CeilingCheck.position, k_CeilingRadius, m_WhatIsGround))
            {
                crouch = true;
            }
        }

        // Set whether or not the character is crouching in the animator
        m_Anim.SetBool("Crouch", crouch);

        //only control the player if grounded or airControl is turned on
        if (m_Grounded || m_AirControl)
        {
            // Reduce the speed if crouching by the crouchSpeed multiplier
            move = (crouch ? move*m_CrouchSpeed : move);

            // The Speed animator parameter is set to the absolute value of the horizontal input.
            m_Anim.SetFloat("Speed", Mathf.Abs(move));

            // Move the character
            m_Rigidbody2D.velocity = new Vector2(move*m_MaxSpeed, m_Rigidbody2D.velocity.y);

            // If the input is moving the player right and the player is facing left...
            if (move > 0 && !m_FacingRight)
            {
                // ... flip the player.
                Flip();
            }
                // Otherwise if the input is moving the player left and the player is facing right...
            else if (move < 0 && m_FacingRight)
            {
                // ... flip the player.
                Flip();
            }
        }
        // If the player should jump...
        if (m_Grounded && jump && m_Anim.GetBool("Ground"))
        {
            // Add a vertical force to the player.
            m_Grounded = false;
            m_Anim.SetBool("Ground", false);
            m_Rigidbody2D.AddForce(new Vector2(0f, m_JumpForce));
        }
    }


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

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

}