UI Image problem, not set to an instance of object

Im working on a game for my 1st year University project, this code works until the player dies, and it's clone respawns (without the public UI Images set in the inspector).

After trying to change the 'stance' console throws hundreds of errors that say "Object reference not set to an instance of an object".

Is anything wrong with this code? I was thinking it might be an issue because I'm not telling the game that the players clone is player and the images should attack to it automatically on respawn.

I had a look at the error online, but it did not quite understand it. (be easy on me i'm kind of new to this) Thanks in advance!

         using UnityEngine;
         using System.Collections;
         using UnityEngine.UI;
     
         public class StanceChanger : MonoBehaviour
         {
         
         float Stance = 0f;
         Animator anim;
         private GameObject monkeyArm;
         // Use this for initialization
     
         public Image Main;
         public Image Bear;
         public Image Cat;
         public Image Monkey;
         
         public Sprite ActiveMainIcon;
         public Sprite ActiveBearIcon;
         public Sprite ActiveCatIcon;
         public Sprite ActiveMonkeyIcon;
     
         public Sprite InactiveMainIcon;
         public Sprite InactiveBearIcon;
         public Sprite InactiveCatIcon;
         public Sprite InactiveMonkeyIcon;
     
         void Awake()
         {
             monkeyArm = GameObject.FindGameObjectWithTag("MonkeyArm");
             monkeyArm.GetComponent<Renderer>().enabled = false;
         }
         void Start()
         {
     
             anim = GetComponent<Animator>();
         }
     
         // Update is called once per frame
         void Update()
         {
             
                   if(Stance != 0)
                 {
                     Main.sprite = InactiveMainIcon;
                 }
                 if(Stance != 1)
                 {
                     Bear.sprite = InactiveBearIcon;
                 }
                 if(Stance != 2)
                 {
                     Cat.sprite = InactiveCatIcon;
                 }
                 if(Stance != 3)
                 {
                     Monkey.sprite = InactiveMonkeyIcon;
                     monkeyArm.GetComponent<Renderer>().enabled = false;
                 }
     
             // No Wings Stance
             if (Input.GetKeyDown(KeyCode.Alpha1))
             {
                 Stance = 0f;
                 anim.SetFloat("StanceChange", Stance);
                 Main.sprite = ActiveMainIcon;
     
             }
             // Bear Stance
             if (Input.GetKeyDown(KeyCode.Alpha2))
             {
                 Stance = 1f;
                 anim.SetFloat("StanceChange", Stance);
                 Bear.sprite = ActiveBearIcon;
             }
             // Cat Stance
             if (Input.GetKey(KeyCode.Alpha3))
             {
                 Stance = 2f;
                 anim.SetFloat("StanceChange", Stance);
                 Cat.sprite = ActiveCatIcon;
     
             }
             //Monkey Stance
             if (Input.GetKey(KeyCode.Alpha4))
             {
                 Stance = 3f;
                 anim.SetFloat("StanceChange", Stance);
                 Monkey.sprite = ActiveMonkeyIcon;
                 monkeyArm.GetComponent<Renderer>().enabled = true;
     
             }
             //Attack
             if (Input.GetKeyDown(KeyCode.F) && Stance == 1f)
             {
     
                 Invoke("Attack", 1); // Invoking attack = slow attack time for animation
             }
         }
     
     }