missingcomponentexception even tho there is an animator attached to trigger

i have done this code

 public class animating : MonoBehaviour
 {
 
     public Animator anim;
 
     // Start is called before the first frame update
     void Start()
     {
         anim = GetComponent<Animator>();
     }
 
     public void OnTriggerEnter(Collider other)
     {
         if (true)
         {
             anim.Play("knockdown_A");
         }
 
     }   
   }
 
 

But even tho when i attach the animator to the gameobject and hit play, it will just uncheck when it triggers, i have been trying to solve this for hours now