C# NullReferenceException Error

So I am trying to create an audio options menu however it is coming up with the following error:

NullReferenceException: Object reference not set to an instance of an object
AudioOptions_Master.Start () (at Assets/Scripts/UI/Standard Menus/Options Menu/Sound/AudioOptions_Master.cs:26)

However, everything is assigned in the inspector.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.UI;
5.  
6. public class AudioOptions_Master : MonoBehaviour
7. {
8.     public Button BTN_MuteMaster;
9.     public Button BTN_TestMaster;
10.  
11.     public Color Color_BTN_Sound;
12.     public Color Color_BTN_Muted;
13.     public Color Color_TXT_Sound;
14.     public Color Color_TXT_Muted;
15.  
16.     public float FLT_Master;
17.     public float FLT_MasterBackup;
18.  
19.     public Slider SLI_Master;
20.  
21.     public Text TXT_Master;
22.     public Text TXT_BTN_MuteMaster;
23.  
24.     public void Start ( )
25.     {
26.         BTN_MuteMaster.onClick.AddListener ( Mute_Master );
27.     }
28.  
29.     public void Mute_Master ( )
30.     {
31.         if ( FLT_Master == 0.0f )
32.         {
33.             // Restore Backup
34.             FLT_Master = FLT_MasterBackup;
35.  
36.             // Change Color
37.             BTN_MuteMaster.GetComponent<UnityEngine.UI.Image> ( ).color = Color_BTN_Sound;
38.         }
39.  
40.         else
41.         {
42.             // Set Backup
43.             FLT_MasterBackup = FLT_Master;
44.  
45.             // Mute Master Audio
46.             FLT_Master = 0.0f;
47.  
48.             // Change Color
49.             BTN_MuteMaster.GetComponent<UnityEngine.UI.Image> ( ).color = Color_BTN_Muted;
50.         }
51.     }
52. }
53.  

 

Surely, BTN_MuteMaster must be null...
Put a break point on line 26 and inspect.
Alternatively just put:

Debug.Log("Is it null? " + (BTN_MuteMaster == null));

before it.

 

Ah found the problem. it was simply a case of having the script on the button as well as the audio handler object I made. Thanks for the help though