title: Why delegate event show NullReferenceException?
body: <p>I follow the tutorial write the code ,but still show this error,the script already attach to the game object
  <a href="https://i.stack.imgur.com/tD4uR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tD4uR.png" alt="Gamecontroller"></a></p>
  
  <p><a href="https://i.stack.imgur.com/7gzsj.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7gzsj.png" alt="GameUI"></a></p>
  
  <p><a href="https://i.stack.imgur.com/3dxHu.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3dxHu.png" alt="Error"></a></p>