I want to serialize an array of custom classes. Is it possible?

Hi. I've read it should be possible however it gives me an error: NullReferenceException: Object reference not set to an instance of an object GameSaver.SaveGame (System.String fileName) (at Assets/GameSaver.cs:39) PlayerController.Update () (at Assets/Scripts/PlayerController.cs:184)

I tried debugging and i can give values to the SaveData class, problem occurs within the array SavedSun[].

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 using System;
 using System.IO;
 using System.Runtime.Serialization.Formatters.Binary;
 
 public class GameSaver : MonoBehaviour {
     private GameObject gameController, timeController, playerController;
 
 
 
     void Awake () {
         DontDestroyOnLoad(gameObject);
     }
 
     public void SaveGame(string fileName){ //get controllers here
         BinaryFormatter ftr = new BinaryFormatter();
         FileStream file = File.Open(Application.persistentDataPath + "/" + fileName + ".dat", FileMode.Open);
 
         gameController = GameObject.FindWithTag ("MainController");
         playerController = GameObject.Find ("PlayerController");
         timeController = GameObject.Find ("TimeController");
 
         SaveData sd = new SaveData();
 
         //data operations here:
         GameObject[] suns = gameController.GetComponent<GameController>().arrayOfSuns;
         sd.randomSeed = gameController.GetComponent<GameController>().randomSeed;
         sd.spaceSize = gameController.GetComponent<GameController>().spaceSize;
         sd.numOfPlayers = gameController.GetComponent<GameController>().numOfPlayers;
 
         sd.year = timeController.GetComponent<TimeController>().year;
         sd.month = timeController.GetComponent<TimeController>().month;
         sd.day = timeController.GetComponent<TimeController>().day;
 
         sd.allSuns = new SavedSun[gameController.GetComponent<GameController>().getStarCount()];
         for (int i = 0; i < sd.allSuns.Length; i++){
             sd.allSuns[i].title = suns[i].GetComponent<OwnerProperties>().getName();
             sd.allSuns[i].owner = suns[i].GetComponent<OwnerProperties>().getOwner();
             sd.allSuns[i].pos = suns[i].transform.position;
             sd.allSuns[i].planets = suns[i].GetComponent<SolarSystem>().getNumPlanets();
             for (int k = 0; k < sd.allSuns[i].planets; k++){
                 GameObject thisPlanet = suns[i].GetComponent<SolarSystem>().getPlanet(k); // initialize planets array
                 sd.allSuns[i].allPlanets[k].climate = thisPlanet.GetComponent<Planet>().getClimate();
                 sd.allSuns[i].allPlanets[k].seed = thisPlanet.GetComponent<Planet>().planetSeed;
                 sd.allSuns[i].allPlanets[k].colonized = thisPlanet.GetComponent<Planet>().colonized;
                 sd.allSuns[i].allPlanets[k].planetMaterial = thisPlanet.GetComponent<Planet>().planetMaterial;
                 sd.allSuns[i].allPlanets[k].resourceValues = thisPlanet.GetComponent<Planet>().resourceValues;
                 sd.allSuns[i].allPlanets[k].bIndexes = thisPlanet.GetComponent<BuildingHandler>().bIndexes;
                 sd.allSuns[i].allPlanets[k].bPositions = thisPlanet.GetComponent<BuildingHandler>().bPositions;
             }
         }
         
         //---------------------
 
         ftr.Serialize(file, sd);
         file.Close();
     }
 
 }
 
 [Serializable]
 class SaveData {
     //player infos
     //fleets, generated objects
 
     public int randomSeed;
     public int spaceSize;
     public int numOfPlayers;
 
     public int year;
     public int month;
     public int day;
     
     public SavedSun[] allSuns;
 
 
 
 }
 
 [Serializable]
 class SavedSun {
     public string title;
     public Vector3 pos;
     public int planets;
     public int owner;
     public SavedPlanet[] allPlanets;
 }
 
 [Serializable]
 class SavedPlanet {
     public string climate;
     public int seed;
     public bool colonized;
     public Material planetMaterial;
     public int[] resourceValues;
     public List<int> bIndexes; //save bSets, OR recreate bSets from positions!
     public List<Vector3>  bPositions;
 }