Please help can't find what is causing this error


i’m not an expert in unity and i got this error in my project.

I searched on google and all i could find was that it is because something is missing??

but i don’t know what’s wrong in my script

the error i get:
( NullReferenceException: Object reference not set to an instance of an object GameMaster.Update() (at Assets/GameMaster.cs:18) )

the script:

Camera.main is a gameObject referance to a camera object with the “MainCamera” tag.

Make sure you have tagged the camera with “MainCamera”

Or make a public GameObject variable and drag drop the camera into the inspector.