Raycast 2D hits sprite with collider, but returns error when not hitting any collider

Hi everyone,

I've been circling around this problem, and I can't find a solution anywhere.

I basically want to do a raycast2D from a touch, and interact with a button (in this particular case, a sprite, with a collider2D component).

I can get the raycast to work, but IF I don't hit the button (anywhere else on screen) I always get an error message saying:

"NullReferenceException: Object reference not set to an instance of an object Touch_Controls.Update () (at Assets/Scripts/Touch_Controls.cs:24)"

For some reason, I can't get the raycast to simply ignore the fact that it's not hitting anything.

I'm guessing this is probably something very simple I'm just overlooking, but it's infuriating. Please help me! :|

Here's my code:

 using UnityEngine;
 using System.Collections;
 
 public class Touch_Controls : MonoBehaviour
 {
     public GUIText tapText;
     public Game_Speed gameSpeedScript;
 
     // Update is called once per frame
     void Update ()
     {
         foreach (Touch touch in Input.touches)
         {
             RaycastHit2D hit = Physics2D.Raycast(Camera.main.ScreenToWorldPoint(touch.position),Vector2.zero);
 
             if (hit.collider.tag == "Button")
             {
                 Debug.Log("Button Activated");
             }
             else
             {
                 Debug.Log("Nothing hit");
             }
         }
 
     }
 }