RPG Mouse targeting error

Hi! Need help. Im making a rpg and i made a C# script.
So i can mark which npc i clicked on. But the problem is the diselect thing.

Code:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class NpcTargeting : MonoBehaviour 
{

    public List<Transform> targets = new List<Transform>();
    public Transform selectedTarget;
    public GameObject myTransform;

    public RaycastHit hit = new RaycastHit();
    public Ray ray;

	// Use this for initialization
	void Start () 
    {
        selectedTarget = null;
	}
	
	// Update is called once per frame
	void Update () 
    {
        
        if (Input.GetKeyDown(KeyCode.Mouse0))
        {
            ray = Camera.main.ScreenPointToRay(Input.mousePosition);
            if (Physics.Raycast(ray, out hit))
            {
                selectedTarget = hit.transform;
                targets.Add(selectedTarget);
                myTransform = hit.transform.gameObject;
            }
        }

        if(selectedTarget != null)
        {
            selectedTarget.Find("Graphic/NpcCircle").gameObject.SetActive(true);
            
        }
        if(selectedTarget == null)
        {
            if(targets.Count == 0)
            {
                myTransform.transform.Find("Graphic/NpcCircle").gameObject.SetActive(false);
            }
        }
        if(targets.Count == 2)
        {
            
            targets.Clear();
            myTransform.transform.Find("Graphic/NpcCircle").gameObject.SetActive(false);
            selectedTarget = null;
        }
       

	}
}

I’ll get an error where it says “UnassignedReferenceException: The variable myTransform of NpcTargeting has not been assigned.”

You can figure this out yourself.

What does your code do when Physics.Raycast returns false. What value does myTransform have? What value does SelectedTarget have?

Walk it through line by line and you will see it.