Calling a function in another script.

I have looked everywhere and cannot find a fix for this. I am trying to run a function that is in another script on my game object, but I keep getting: NullReferenceException: Object reference not set to an instance of an object GUIButton.OnGUI () (at Assets/Scripts/GUIButton.cs:29)

I have checked everything and cannot figure out why it is throwing this exception. Here is the script I am running: using UnityEngine; using System.Collections;

 public class GUIButton : MonoBehaviour {
 
     public Texture2D texture;
     public GameObject guiObject;
 
     private Camera cam;
     private Rect button;
     private GameObject cam1;
     private GameObject cam2;
 
     void Start() {
         cam1 = GameObject.Find("1st Person");
         cam2 = GameObject.Find("3rd Person");
         cam = cam1.camera;
         if (cam1.activeSelf == true) {
             cam = cam1.camera;
         } else if (cam2.activeSelf == true) {
             cam = cam2.camera;
         }
         GUITexture gui = guiObject.GetComponent<GUITexture>();
         button = gui.GetScreenRect(cam);
     }
 
     void OnGUI() {
         if (GUI.Button(button, texture)) {
             (guiObject.GetComponent("Action") as Action).Activate(guiObject);
         }
     }
 }

And here is the script that contains the function I am accessing:

 using UnityEngine;
 using System.Collections;
 
 public class Action : MonoBehaviour {
 
     private GameObject bob;
     private GameObject cam1;
     private GameObject cam2;
 
     void Start () {
         bob = GameObject.Find("Bob");
         cam1 = GameObject.Find("1st Person");
         cam2 = GameObject.Find("3rd Person");
     }
     
     public void Activate(GameObject obj) {
         if (obj.name == "Exit To Main Menu") {
             Resume();
         } else if (obj.name == "Options") {
             OpenOptions();
         } else if (obj.name == "Resume") {
             MainMenu();
         }
     }
 
     private void Resume() {
         GameObject.Find("In-Game Menu").SetActive(false);
         (bob.GetComponent("Character Motor") as CharacterMotor).enabled = true;
         (bob.GetComponent("FPSInput Controller") as FPSInputController).enabled = true;
         (bob.GetComponent("Mouse Look") as MouseLook).enabled = true;
         (cam1.GetComponent("Mouse Look") as MouseLook).enabled = true;
         (cam2.GetComponent("Mouse Look") as MouseLook).enabled = true;
     }
     
     private void OpenOptions() {
         
     }
     
     private void MainMenu() {
         
     }
 }

Any and all help is appreciated.