IndexOutOfRangeException

I've been getting the IndexOutOfRangeException error on occasions which I can't seem to predict. The script will run fine after several times running but then out of nowhere it will throw this error out. "IndexOutOfRangeException: Array index is out of range."

 var platformColliders : Collider[] = Physics.OverlapSphere(transform.position,3, layerPlatform);
 var platform : GameObject = platformColliders[Random.Range(0,platformColliders.Length)].gameObject;