Why does my null reference become instantiated?

I create an array of Player with length of 2. I instantiate 1 of the 2 Player references and I set the other one to null. I run the game, and, as expected, I get alternating Logs of "100" and "NULL". If I go to Visual Studio and edit the script (i.e. add and then remove a blank line), then when I go back to Unity, I only get Logs of "100" for both Player objects. Why does players[0] become instantiated?

 using UnityEngine;
 using System.Collections;
 
 public class Test : MonoBehaviour {
 
    Player[] players;
 
    void Start()
    {
       players = new Player[2];
       players[0] = null;
       players[1] = new Player();
    }
 
    void Update()
    {
       for (int i = 0; i < 2; i++)
       {
          if (players[i] == null)
          {
             Debug.Log("NULL");
          }
          else
          {
             Debug.Log(players[i].health);
          }
       }
    }
 }
 
 [System.Serializable]
 public class Player
 {
    public int health = 100;
 }