How do I check a List[0], when it's nothing?

I have made this function (inspired by the bugzerg arcade hack'n'slash tutorial)

         public static GameObject ClosestGameObject (string searchTag, Transform ClosestTo)
         {
             List<Transform> outPutList = new List<Transform>(); 
             outPutList.Clear();
             GameObject[] go = GameObject.FindGameObjectsWithTag(searchTag);
             foreach(GameObject goes in go)
             {
                 outPutList.Add(goes.transform);
             }
             outPutList.Sort(delegate(Transform t1, Transform t2) {
                     return Vector3.Distance(t1.position, ClosestTo.position).CompareTo(Vector3.Distance(t2.position, ClosestTo.position));
             });
             GameObject output = outPutList[0].gameObject;
             return output;
         }

But if I feed it a searchTag that isnt on any of the gameObjects in the scene, it gives me an error at line 13: Argument is out of range. Is there any way to check if the go variable contain anything? I know I can't just simply write

 GameObjecy[] go = GameObject.FindGameobjectsWithTag("Bleh");
 if(go != null)
 {
     // do stuff
 }
 else
 {
     return null;
 }

-thanks in advance :)