Having issues with a NullReferenceException error. Code does as expected in some instances but I receive the error in others. Debugger directs me to line where if(hit.collider.tag == (DestructibleCube")).

 using UnityEngine;
 using System.Collections;
 using UnityEngine.EventSystems;
 
 public class TimeDestroy : MonoBehaviour {
     public GameObject bombToDestroy;
     public GameObject explosion;
     public GameObject CubeExplosion;
     public int PowerUpLevel;
    
 
     private float timeLeft = 4;
     // Use this for initialization
     
     
     // This is a 4 second time to have bombs blow up.
     void FixedUpdate ()
     {
         //sets time on instantiated object(dropped bomb) which explodes after 4 seconds
         timeLeft -= Time.deltaTime;
      if ( timeLeft < 0)
         {
             CastFwd(); 
             CastBack();
             CastLeft();
             CastRight();
             
 
             Instantiate(explosion, transform.position, transform.rotation); // graphic for explosion
             Destroy(bombToDestroy, 0f); //removes instantiated bomb
             Bomb_Pickup.bombcount += 1;
             
         }
     }
 
 
     void CastFwd() // Casts a ray in the forward direction to interact with cubes
     {
         
         RaycastHit hit;
         Ray landingRay = new Ray(transform.position, Vector3.forward);
         Debug.DrawRay(transform.position, Vector3.forward);
         Debug.Log("1");
         if (Physics.Raycast(landingRay, out hit, (.3f + (PowerUpLevel * .2f))));
         {
             Debug.Log("2");
             if (hit.collider.tag == ("DestructibleCube")) //checks for if raycast hits collider with tag 
             {
                 Debug.Log("3");
                 Instantiate(CubeExplosion, hit.collider.gameObject.transform.position, Quaternion.identity); //replaces gameobject with a fragmented gameobject to explose
                 hit.collider.gameObject.SetActive(false); //deactivates original gameobject
             }
         }
     }