Question what is the problem?

I want to score up if bird go through tunnel.
But I have this error. and no score-up.

NullReferenceException: Object reference not set to an instance of an object
Score.Update () (at Assets/Score.cs:20)

score.cs

using System.Collections;
using System.Collections.Generic;
using TMPro;
using UnityEngine;
using UnityEngine.UI;
public class Score : MonoBehaviour
{
public static int score = 0;
// Start is called before the first frame update
void Start()
{

}
// Update is called once per frame
void Update()
{
GetComponent<Text>().text = score.ToString(); // str(score) < -- 20 line
}
}

Scoreup.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class scoreup : MonoBehaviour
{
private void OnTriggerEnter2D(Collider2D collision)
{
Score.score++;
}
}