So, i am making a save load scene system that loads data into a .txt file which holds each object. I have a few objects that can be interacted with and they have a script which contains a “ConnectedObjects” List. but it keeps coming up with the error in the title. this is only when loading the scene. here is a part of the code.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.IO;

public class LoadLevelSystem : MonoBehaviour
{

    string[] objectsToLoad;

    string path = Application.dataPath + "/Scene.txt";
    int propertyID;

    Vector3 objectPos;
    Quaternion objectRot;
    int objectPrefabID;
    int indevObjectID;
    public List<int> connectedObjects = new List<int>();


    public GameObject levelGO;

    public GameObject[] objectsToPlace;

    public void ReadScene() {
        objectsToLoad = File.ReadAllLines(path);

        foreach(string line in objectsToLoad) {
            string[] properties = line.Split("|");
            foreach (string property in properties) {
                propertyID += 1;
                Debug.Log(property);
                if (propertyID == 1) {
                    string properti = property.Replace("(", "");
                    properti = properti.Replace(")", "");
                    string [] indevidualNumberStrings = properti.Split(", ");
                    objectPos.x = float.Parse(indevidualNumberStrings[0]);
                    objectPos.y = float.Parse(indevidualNumberStrings[1]);
                    objectPos.z = float.Parse(indevidualNumberStrings[2]);
                } else if (propertyID == 2) {
                    string properti = property.Replace("(", "");
                    properti = properti.Replace(")", "");
                    string [] indevidualNumberStrings = properti.Split(", ");
                    objectRot = Quaternion.Euler(
                        float.Parse(indevidualNumberStrings[0]),
                        float.Parse(indevidualNumberStrings[1]),
                        float.Parse(indevidualNumberStrings[2])
                    );
                } else if (propertyID == 3) {
                    objectPrefabID = int.Parse(property);
                } else if (propertyID == 4) {
                    indevObjectID = int.Parse(property);
                } else if (propertyID == 5) {
                    string properti = property.Replace("(", "");
                    properti = properti.Replace(")", "");
                    string [] indevidualNumberStrings = properti.Split(", ");
                    foreach (string numberString in indevidualNumberStrings) {
                        connectedObjects.Add(int.Parse(numberString));
                    }
                }
            }
            propertyID = 0;
            GameObject obj = Instantiate(objectsToPlace[objectPrefabID], objectPos, objectRot);
            obj.GetComponent<identifier>().individualObjectID = indevObjectID;
            obj.transform.parent = levelGO.transform;
            foreach (int connectedObjectIndevID in connectedObjects) {
                foreach(Transform childObj in levelGO.transform) {
                    if (childObj.gameObject.GetComponent<identifier>().individualObjectID == connectedObjectIndevID) {
                        if (obj.GetComponent<identifier>().ID == 0){
                            childObj.gameObject.GetComponent<interactableScript>().connectedObjects.Add(childObj.gameObject);
                        } 
                        
                        if (obj.GetComponent<identifier>().ID == 2){
                            childObj.gameObject.GetComponent<buttonScript>().connectedObjects.Add(childObj.gameObject);
                        }
                    }
                }
            }
        }
    }
}

I am trying to get the connectedObjects List to add the object to the list but i cant getting working i have tried for like 2 hours. this is my last resort.