How to check variable on obj I triggered

Hi I'm doing a game whre you have randomly generated dungeon and I want to check if the spawnpoint that spawns rooms has variable "spawned" set to false. I used GetComponent to do this and it is giving me "NullReferenceException" error. Is there anyone who could help me?
I'm following this tutorial to do the dungeon generation:

And I'm getting that error after he coded the closedRoom spawn part.

Code (CSharp):

1.  
2. void OnTriggerEnter(Collider other)
3.     {
4.         roomSpawner = other.gameObject.GetComponent<RoomSpawner>();
5.         if (other.CompareTag("SpawnPoint"))
6.         {
7.           if(other.GetComponent<RoomSpawner>().spawned == false && spawned == false)
8.             {
9.                 Instantiate(templates.closedRoom[1], transform.position, Quaternion.identity);
10.                 Destroy(gameObject);
11.             }
12.             spawned = true;
13.         }
14.  
15.  
16.