NullReferenceException: Object reference not set to an instance of an object. I have tried to fix. PlayerHUD works but EnemyHUD does not

Question

I'm getting this error message whenever I press play:

NullReferenceException: Object reference not set to an instance of an object BattleSystem+<SetupBattle>d__14.MoveNext () (at Assets/BattleSystem.cs:54) UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <2a3b1fc140ae44e9a4476e34a2a29726>:0) UnityEngine.MonoBehaviour:StartCoroutine(IEnumerator) BattleSystem:Start() (at Assets/BattleSystem.cs:36)

This is my code:

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

public enum BattleState { START, PLAYERTURN, ENEMYTURN, WON, LOST }


public class BattleSystem : MonoBehaviour
{

    public GameObject playerPrefab;
    public GameObject enemyPrefab;

    public Transform playerBattleStation;
    public Transform enemyBattleStation;

    Unit PlayerUnit;
    Unit EnemyUnit;

    public Text dialogueText;

    public Button Attack;
    public Button Heal;
    public Button Block;

    public BattleHUD PlayerHUD;
    public BattleHUD EnemyHUD;

    public BattleState state;

    // Start is called before the first frame update
    void Start()
    {
        state = BattleState.START;
        StartCoroutine(SetupBattle());
    }

    IEnumerator SetupBattle()
    {
        //instantiate player and enemy GameObjects
        GameObject playerGO = Instantiate(playerPrefab, playerBattleStation);
        PlayerUnit = playerGO.GetComponent(typeof(Unit)) as Unit;

        GameObject enemyGO = Instantiate(enemyPrefab, enemyBattleStation);
        EnemyUnit = enemyGO.GetComponent(typeof(Unit)) as Unit;

        if (EnemyUnit == null)
        {
            Debug.LogError("No EnemyUnit component found");
        }

        PlayerHUD.SetHUD(PlayerUnit);
        EnemyHUD.SetHUD(EnemyUnit);

I tried to change the code slightly to see if it would work any other way. I'm new to unity and c# so I'm not 100% sure how to fix this. Please help me.