object reference not set to an instance of an object error

hi, so im trying to make a waypoint marker but however, it's givinthe object reference null error. how do i fix it? here is my code:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.UI;
5.  
6. public class WaypointScript : MonoBehaviour
7. {
8.    
9.     public Image img;
10.    
11.     public Transform target;
12.     // UI Text to display the distance
13.     public Text meter;
14.     // To adjust the position of the icon
15.     public Vector3 offset;
16.  
17.     private void Update()
18.     {
19.      
20.         float minX = img.GetPixelAdjustedRect().width / 2;
21.        
22.         float maxX = Screen.width - minX;
23.  
24.        
25.         float minY = img.GetPixelAdjustedRect().height / 2;
26.        
27.         float maxY = Screen.height - minY;
28.  
29.      
30.         Vector2 pos = Camera.main.WorldToScreenPoint(target.position + offset);
31.  
32.         //check if behind
33.         if (Vector3.Dot((target.position - transform.position), transform.forward) < 0)
34.         {
35.            
36.             if (pos.x < Screen.width / 2)
37.             {
38.                
39.                 pos.x = maxX;
40.             }
41.             else
42.             {
43.                
44.                 pos.x = minX;
45.             }
46.         }
47.  
48.         pos.x = Mathf.Clamp(pos.x, minX, maxX);
49.         pos.y = Mathf.Clamp(pos.y, minY, maxY);
50.  
51.        
52.         img.transform.position = pos;
53.        
54.         meter.text = ((int)Vector3.Distance(target.position, transform.position)).ToString() + "m";
55.     }
56. }

 

Maybe post error? it says you on what line in code is it

 

Code (CSharp):

1.  Vector2 pos = Camera.main.WorldToScreenPoint(target.position + offset);

it says line 30

 

So you "target" is null, did you set it in inspector?

 

yes, if this is what you meant

 

Check your camera, you probably don't have any cameras with the tag "MainCamera".

 

The answer is always the same... ALWAYS. It is the single most common error ever.

Don't waste your life spinning around and round on this error. Instead, learn how to fix it fast... it's EASY!!

Some notes on how to fix a NullReferenceException error in Unity3D
- also known as: Unassigned Reference Exception
- also known as: Missing Reference Exception
- also known as: Object reference not set to an instance of an object

http://plbm.com/?p=221

The basic steps outlined above are:
- Identify what is null
- Identify why it is null
- Fix that.

Expect to see this error a LOT. It's easily the most common thing to do when working. Learn how to fix it rapidly. It's easy. See the above link for more tips.

This is the kind of mindset and thinking process you need to bring to this problem:

https://forum.unity.com/threads/why-do-my-music-ignore-the-sliders.993849/#post-6453695

Step by step, break it down, find the problem.