Enemy not able to update score when destroyed.

I have a Null Reference exception on my enemy, it's a prefab and it's instantiated in a spawn object it's also derived from a list. I took the enemy out and added the characterStats object it was asking for, I saved it and then played game again error still persists. Any help would be appreciated.

Here is the code. using System.Collections; using System.Collections.Generic; using UnityEngine;

 [RequireComponent(typeof(AudioSource))]
 
 public class FootDoDamage : MonoBehaviour
 {
 
 
     GameManager gameManager;
     CharacterStats characterStats;
     PlayerController playerController;
     public Animator anim;
     public GameObject explosionPrefab;
 
     public AudioSource footExplosionSound;
 
 
     public EnemySight enemySight;
     public GameObject punchAttackObj;
     public GameObject kickAttackObj;
 
     public int footHealth = 100;
     public int footScore = 1;
 
     void Start()
     {
 
 
    
 
         if (explosionPrefab ==null)
         {
             explosionPrefab = GetComponent<GameObject>();
         }
         
         if(footExplosionSound == null)
         {
             footExplosionSound = GetComponent<AudioSource>();
         }
         
         footExplosionSound = GetComponent<AudioSource>();
 
 
         if (anim == null)
         {
             anim = GetComponent<Animator>();
         }
 
         if (playerController == null)
         {
             playerController = GetComponent<PlayerController>();
         }
 
         if (enemySight == null)
         {
             enemySight = GetComponent<EnemySight>();
         }
 
         if (gameManager == null)
         {
             gameManager = GetComponent<GameManager>();
 
         }
         
          if(characterStats == null)
         {
             characterStats = GetComponent<CharacterStats>();
 
         }
 
 
       
         
     }
 
     // Update is called once per frame
     void Update()
     {
    
 
     }
 
 
 
     public void HidePunchAttack()
     {
         enemySight.anim.SetBool("attackcombo", false);
         punchAttackObj.SetActive(false);
     }
 
     public void ShowPunchAttack()
     {
         enemySight.anim.SetBool("attackcombo", true);
         punchAttackObj.SetActive(true);
     }
 
     public void HideKickAttack()
     {
         enemySight.anim.SetBool("attackcombo", false);
 
         kickAttackObj.SetActive(false);
     }
 
     public void ShowKickAttack()
     {
         enemySight.anim.SetBool("attackcombo", true);
 
         kickAttackObj.SetActive(true);
     }
   
     public void FootTakeDamage()
     {
 
         //if (this.gameObject != null)
         if(GameObject.Find("FootSolder(Clone)"))
             {
                 // Taking away health based on sword attack
                 footHealth -= 25; // take away 50 from attack
             
             anim.SetBool("hit", true);
             anim.SetBool("attackcombo", false);
             anim.SetBool("walk", false);
             gameObject.SetActive(true);
 
             if (footHealth <= 0)
             {
                 characterStats.AddScore();
                 anim.SetBool("hit", false);
                 anim.SetBool("defeated", true);
                 CancelInvoke("FootSolder");
                 StartCoroutine(HideFootSolder()); // Call the coroutine here and hide object
 
                 enemySight.navMeshAgent.updateRotation = false;
                 enemySight.navMeshAgent.angularSpeed = 0;
                 enemySight.navMeshAgent.isStopped = true;
                //enemySight.navMeshAgent.enabled = false;
             }
         }
        
 
 
     }
     // Hide object in Coroutine instead of out right destroying it and causing errors.
     IEnumerator HideFootSolder()
     {
         //There was a major Missing Component exception and it seemed to be fixed.
         yield return new WaitForSeconds(1.5f);
 
         try { 
               footExplosionSound.Play();
               Instantiate(explosionPrefab, transform.position, Quaternion.identity);
               //Destroy(gameObject, 1.5f);
               gameObject.SetActive(false);
 
               //GetComponent<CapsuleCollider>().enabled = false;
               // GetComponent<CharacterController>().enabled = false;
 
             }
 
             catch (MissingComponentException)
             {
                 footExplosionSound = FindObjectOfType<AudioSource>();
 
             }
 
     }
 
     void OnTriggerEnter(Collider other)
     {
         if (other.tag == "lkatana" || other.tag == "rkatana" || other.tag == "leorfootattack")
         {
             FootTakeDamage();
          
             // To Do Get the Blocked Colliders to turn off when players are defeated
             print("Leo is hitting FootSolder.");
         }
       
     }
 
   
 }
 
 
 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityStandardAssets.Utility;
 
 public class Enemies : MonoBehaviour {
 
 
     public Transform []spawnPosition;
     public GameObject footPrefab; //footPrefab2, //footPrefab3;
     public List<Transform> enemiesSpawned = new List<Transform>();
 
     public FollowTarget followTarget;
     public CameraFollow cameraFollow;
     public GameObject blockColliders;
 
     public bool wave1;
     public bool wave2;
     public bool wave3;
 
     public int spawnRateMax = 6;
     public int spawnRateMin = 1;
     public float spawnTime = 3f;
 
     public float countdown;
     private float currentTime;
 
 
     // Use this for initialization
     void Awake ()
     {
         currentTime = countdown;
 
        // InvokeRepeating("Wave1Attack", spawnTime, spawnTime);
 
         if(cameraFollow == null)
         {
             cameraFollow = GetComponent<CameraFollow>();
 
         }
 
 
         if(blockColliders ==null)
         {
             blockColliders = GetComponent<GameObject>();
         }
 
 
         if(followTarget == null)
         {
             followTarget = GetComponent<FollowTarget>();
 
         }
     }
     
        
     // Update is called once per frame
     void Update ()
     {
 
       
         /*
         countdown -= Time.deltaTime;
 
         if(countdown <= 0)
         {
             wave1 = true;
              Wave1Attack();
 
             // camera stops following player when a wave is on
             cameraFollow.enabled = false;
             wave1 = false;
 
             //print("time is up.");
         }
 
         else
         {
             wave1 = false;
             CancelInvoke("Wave1Attack");
             cameraFollow.enabled = true;
         }
         */
 
         /*
         if(wave1 )
         {
             wave1 = true;
             Wave1Attack();
         }
 
         if(!wave1)
         {
             wave1 = false;
             CancelInvoke("Wave1Attack");
         }
          */
     }
 
 
     public void BlockCollidersOn()
     {
         blockColliders.SetActive(true);
         followTarget.enabled = true;
     }
 
     public void BlockCollidersOff()
     {
         blockColliders.SetActive(false);
         followTarget.enabled = false;
     }
 
 
 
     public void SpawnEnemies()
       {
           int ranValue = Random.Range(spawnRateMin, spawnRateMax +1);
 
           for (int i = 0; i < ranValue; i++)
           {
               int ranSpawn = Random.Range(0, spawnPosition.Length);
               GameObject go = Instantiate(footPrefab, spawnPosition[ranValue].position, Quaternion.identity) as GameObject;
               enemiesSpawned.Add(go.transform);
           }
       }
       
 
 
   /*
     public void Wave1Attack()
     {
       
         int spawnPointIndex = Random.Range(0, spawnPosition.Length);
 
         Instantiate (footPrefab, spawnPosition[spawnPointIndex].position, spawnPosition[spawnPointIndex].rotation);
     }
     */
    }