Need Help with a Null Reference

Error : NullReferenceException: Object reference not set to an instance of an object PoisonCloudHealthAdjustment.OnTriggerStay (UnityEngine.Collider other) (at Assets/Scripts/PoisonCloudHealthAdjustment.cs:16)

     using UnityEngine;
     using System.Collections;
     
     public class PoisonCloudHealthAdjustment : MonoBehaviour {
         
         IEnumerator TriggerPause(int wait, GameObject pauseObject)
         {
             pauseObject.collider.enabled = false;
             yield return new WaitForSeconds(wait);
             pauseObject.collider.enabled = true;
             
         }
         void OnTriggerStay(Collider other){
             if(other.tag == "Player" )
             {
                 if(gameObject.GetComponent<CreatePlatforms>().gameMode == 2) gameObject.GetComponent<PlayerHealth>().curHealth -= 1;
                 StartCoroutine( TriggerPause(2, gameObject) );
             }
         }
         void Start()
         {
             StartCoroutine( TriggerPause(1, gameObject) );
         }
     }

Is the Coroutine messing up the collider or something?

Thanks :)