NullReferenceException Object reference not set to an instance of an object (733325)

Unity Engine
1 
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.AI;
using Complete;

public class StateController : MonoBehaviour
{

    public State currentState;
    public EnemyStats enemyStats;
    public Transform eyes;
    public State remainState;


    [HideInInspector] public NavMeshAgent navMeshAgent;
    [HideInInspector] public Complete.TankShooting tankShooting;
    [HideInInspector] public List<Transform> wayPointList;
    [HideInInspector] public int nextWayPoint;
    [HideInInspector] public Transform chaseTarget;
    [HideInInspector] public float stateTimeElapsed;

    private bool aiActive;


    void Awake()
    {
        tankShooting = GetComponent<Complete.TankShooting>();
        navMeshAgent = GetComponent<NavMeshAgent>();
    }

    public void SetupAI(bool aiActivationFromTankManager, List<Transform> wayPointsFromTankManager)
    {
        wayPointList = wayPointsFromTankManager;
        aiActive = aiActivationFromTankManager;
        if (aiActive)
        {
            navMeshAgent.enabled = true;
        }
        else
        {
            navMeshAgent.enabled = false;
        }
    }

    void Update()
    {
        if (!aiActive)
      
            return;
            currentState.UpdateState(this);
      
    }

    void OnDrawGizmos()
    {
        if (currentState != null && eyes != null)
        {
            Gizmos.color = currentState.sceneGizmoColor;
            Gizmos.DrawWireSphere(eyes.position, enemyStats.lookSphereCastRadius);
        }
    }

    public void TransitionToState(State nextState)
    {
        if (nextState != remainState)
        {
            currentState = nextState;
         
        }
    }

}

Can someone tell me what is wrong with my code? I just started coding with C#. Unity says the error is on line 51.

2

It’s telling you the error, you have a null/missing/unassigned reference.

Did you drag and drop the object of ‘currentState’ in the inspector?