checking if gameobject exists

Hi. I use this code to deactivate gameobjects.

 GameObject[] rigid;
 void Start()        
   rigid = GameObject.FindGameObjectsWithTag("klocek");
     foreach(GameObject rigids in rigid)
     {
         if(rigids.transform.position.x>30)
         rigids.SetActive(false);
     }
 }

And then I need to activate them somewhen

 void Update(){
   foreach(GameObject rigids in rigid)
   {
     if(rigids.transform.position.x<p1)// if its time to activate you
     rigids.SetActive(true);
   }
 }

Everything works untill some of objects get Destroyed. Then I take error: Trying to access gameobject than doesnt exist. Is there a way to avoid this?