One of my game buttons is giving errors, even though second button with same code works fine?

Hi all,
I am making two buttons in my game, in w$$anonymous$$ch one button plays "Spin Attack" animation and other "Double Chop" animation. I have added two separate functions to each button but with exact same code (can see in the code sample below). When I press the Attack Button (AttackButton() function is added to it) in the Unity, it works fine.

But when I press the Spin Attack button (to w$$anonymous$$ch SpinButton() function is added to it), its throwing error :-

UnassignedReferenceException: The variable anim of PlayerControllerAndroid has not been assigned. You probably need to assign the anim variable of the PlayerControllerAndroid script in the inspector.

I have assigned anim variable in the script as you can see in the code and Player Component has been added to it, then why is it throwing t$$anonymous$$s error? Yes, "SpinAttack" and "DoubleChop" are genuine and correct Animation names here. I am stuck on t$$anonymous$$s issue for a w$$anonymous$$le now, it seems basic problem but please do help!

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class PlayerControllerAndroid : MonoBehaviour
 {
     
     [SerializeField] private float moveSpeed = 10.0f;
     [SerializeField] private LayerMask layerMask;
     [SerializeField] private FixedJoystick joystick;
 
     private CharacterController charachterController;
     private Vector3 currentLookTarget = Vector3.zero;
     private Animator anim;
     private BoxCollider[] swordColliders;
     private GameObject fireTrail;
     private ParticleSystem fireTrailParticles;
     // Start is called before the first frame update
     void Start()
     {
         charachterController = GetComponent <CharacterController> ();
         anim = GetComponent <Animator> ();
         swordColliders = GetComponentsInC$$anonymous$$ldren <BoxCollider> ();
         fireTrail = GameObject.FindWithTag("Fire") as GameObject;
         fireTrail.SetActive(false);
     }
 
     // Update is called once per frame
     void Update()
     {
         if(!GameManager.instance.GameOver)
         {
             Vector3 moveDirection = new Vector3(joystick.Horizontal,0,joystick.Vertical);
             charachterController.SimpleMove (moveDirection*moveSpeed);
 
             if(moveDirection == Vector3.zero)
             {
                 anim.SetBool("IsWalking",false);
             }else{
                 anim.SetBool("IsWalking",true);
             }     
         }
     }
 
     void FixedUpdate()
     {
         Vector3 joystickPosition = new Vector3(joystick.Horizontal,0,joystick.Vertical);  
            
         Quaternion rotation = Quaternion.LookRotation(joystickPosition);
         transform.rotation = Quaternion.Lerp(transform.rotation,rotation,Time.deltaTime*10f);       
     }
 
 
     public void BeginAttack()
     {
         foreach (var weapon in swordColliders)
         {
             weapon.enabled = true;
         }
     }
     
     public void EndAttack()
     {
         foreach (var weapon in swordColliders)
         {
             weapon.enabled = false;
         }
     }
 
     public void speedPowerUp()
     {
         StartCoroutine(fireTrailRoutine());
     }
 
     IEnumerator fireTrailRoutine()
     {
         fireTrail.SetActive(true);
         moveSpeed = 13f;
         yield return new WaitForSeconds(10f);
         moveSpeed = 6f;
         fireTrailParticles = fireTrail.GetComponent<ParticleSystem> ();
         var em = fireTrailParticles.emission;
         em.enabled = false;
         yield return new WaitForSeconds(3f);
         em.enabled = true;
         fireTrail.SetActive(false);
     }
 
     public void SpinButton()
     {
         if(!GameManager.instance.GameOver)
             anim.Play("SpinAttack");            
     }
 
     public void AttackButton()
     {
         if(!GameManager.instance.GameOver)
             anim.Play("DoubleChop");
     }
 }