RuntimeAnimatorController becomes null for no reason

I am trying to make an Equip weapon system, but whenever I Instantiate my weapon, the runtimeAnimatorController becomes null.

     void Update() {
         for (int key = 0; key < slotAmount; key++) {
             int keyName = key + 1;
                 
             if (Input.GetKeyDown(keyName.ToString()) && equippedSlot != key) {
                 invController.AddInventoryItem (PlayerController.Instance.itemDatabase.Item (0), 1);
 
                 equipmentSlots [0 ].InvItem = invController.GetInventoryItem (0);
                 EquipWeapon (equipmentSlots[key], key);
             } else if (Input.GetKeyDown(keyName.ToString()) && equippedSlot == key) {
                 DequipWeapon (equipmentSlots[key], key);
             }
         }
     }
 
     void EquipWeapon(EquipmentSlot slot, int index) {
         if (slot.InvItem != null) {
             Item item = slot.InvItem.Item;
 
             GameObject weapon = item.Prefab;
             GameObject newWeapon = Instantiate (weapon, playerHandle) as GameObject;    
 
             slot.WeaponObject = newWeapon;
 
             newWeapon.transform.localPosition = new Vector3 (0f, 0f, 0f);
             newWeapon.transform.localRotation = Quaternion.Euler (0f, 180f, 0f);
 
             rightArmAnimator.runtimeAnimatorController = item.AnimOverride;
 
             equippedSlot = index;
         }
     }

And then after I equip the weapon, the runtimeAnimatorController becomes null: