Can't update score text - small error breaks the game (Space Shooter Tutorial)

I'm at the final stages of the tutorial, but now that I've tried to add the Score Text to work, I've been getting the following error:

NullReferenceException: Object reference not set to an instance of an object GameController.UpdateScore () (at Assets/Scripts/GameController.cs:49) GameController.Start () (at Assets/Scripts/GameController.cs:21)

I checked in the Inspector, and the scoreText seems appropriately assigned, but when I start playing the game, it gets switched to "None".

This is my code. What am I missing?

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 
 public class GameController : MonoBehaviour {
 
     public GameObject asteroid;
     public int hazardCount; // Number of hazards per wave
 
     public float startWait;
     public float spawnWait;
     public float waveWait;
 
     private int score;
     public Text scoreText;
 
     void Start()
     {
         scoreText = GetComponent<Text>();
         score = 0;
         UpdateScore();
     }
     
     public void AddScore(int x)
     {
         score += x;
         UpdateScore();
     }
 
     void UpdateScore()
     {
         scoreText.text = "Score: " + score;
     }
 }