I created a system that tracks number of matches have

so I have a system that add matches when I pick them and removes them when you light a candle, and when you run out you can no longer light candles. I have a UI script that supposed to display a updated number based on match count. every part works except the unity display

I keep getting this error : NullReferenceException: Object reference not set to an instance of an object FirstPerson.AddMatches (System.Single matches) (at Assets/MyScript/FirstPerson.cs:64) PickupMatch.OnTriggerStay (UnityEngine.Collider target) (at Assets/MyScript/PickupMatch.cs:1

pickupmatch Script:

 void OnTriggerStay(Collider target)
     {
         if (target.tag == "Player")
         {
             if (Input.GetKeyDown(KeyCode.E))
             {
                 txt.text = " ";
                 match.SetActive(false);
                 FirstPerson.AddMatches(5);
             }
         }
     }

FirstPerson Script

  [Header("Matches Parameters")]
     [SerializeField] private static float currentmatches;
     private static UIScript uiscript;
     void Start()
     {
         UIScript uiscript = GetComponent<UIScript>();
     }
     public static void AddMatches(float matches)
     {
         
         currentmatches = currentmatches + matches;
         uiscript.UpdateMatches(currentmatches);
     }
     public static void MinusMatches(float matches)
     {
         currentmatches = currentmatches - matches;
     }
     public static float GetMatches()
     {
         return (currentmatches);
     }

lightacandle

 void OnTriggerStay(Collider target)
     {
         matches = FirstPerson.GetMatches();
 
         if (target.tag == "Player")
         {
             if (Input.GetKeyDown(KeyCode.E) && matches > 0)
             {
                 txt.text = " ";
                 fire1.SetActive(true);
                 FirstPerson.MinusMatches(1);
             }
         }
     }

UI script

 [SerializeField] private TextMeshProUGUI healthText = default;
     [SerializeField] private TextMeshProUGUI staminaText = default;
     [SerializeField] private TextMeshProUGUI matchText = default;
     private float matches;
 
     private void OnEnable()
     {
         FirstPerson.OnDamage += UpdateHealth;
         FirstPerson.OnHeal += UpdateHealth;
         FirstPerson.OnStaminaChange += UpdateStamina;
         UpdateMatches(matches);
     }
 
     private void OnDisable()
     {
         FirstPerson.OnDamage -= UpdateHealth;
         FirstPerson.OnHeal -= UpdateHealth;
         FirstPerson.OnStaminaChange -= UpdateStamina;
     }
 
     private void Start()
     {
         UpdateHealth(100);
         UpdateStamina(100);
         matches = 0;
     }
 
     private void UpdateHealth(float currentHealth)
     {
         healthText.text = currentHealth.ToString("00");
     }
 
     private void UpdateStamina(float currentStamina)
     {
         staminaText.text = currentStamina.ToString("00");
     }
 
     public void UpdateMatches(float currentmatch)
     {
         matchText.text = currentmatch.ToString("00");
     }
 }