ArgumentNullException: Argument cannot be null. _need help!

Scripting
1

i have a scene to register, then another scene to play, and the last one is the ranking scene. But when i try to jump from the register scene, to the ranking scene to see the score without register first.
It says (ArgumentNullException: Argument cannot be null. Parameter name: s

How can i fox this error, to allow me see the ranking scene first before play.

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

public class AddScore : MonoBehaviour {

    void Start(){
        AddPScore (0);
    }
    void AddPScore(int storeResult){
        WWWForm form = new WWWForm ();
        form.AddField ("user", LoginSystem.userName);
        form.AddField ("score", storeResult);
        WWW w = new WWW ("https://nfx.000webhostapp.com/AddScore.php",form);
        StartCoroutine (receive (w));
        Debug.Log("funcionou");
    }
    IEnumerator receive(WWW w){
        yield return w;
        if (w.error == null) {
        }
    }

}
2

No clue, you’re not doing anything with scene changes nor do I know where your error is. You’re just showing some form to add score to something.

Only guess is if your error is happening in that method that your LoginSystem.userName or your storeResult is null, thus you get an error. If these are required, then you can’t save it or you have to come up with something to be passed in if a user chooses not to register.