"NullReferenceException: Object reference not set to an instance of an ..." when accessing property

Unity Engine
1

Hello,
I’m a beginner in Editor Scripting. I’ve written two scripts - ‘CalculateStats.cs’ and ‘CalculateStatsEditor.cs’.
CalculateStats.cs contains some properties that I’ve created. CalculateStatsEditor.cs is basically editor script that accesses those properties. Whenever I attach CalculateStats.cs to the MainCamera, I get a NullReferenceException on Line 13 in ‘CalculateStats.cs’. If the script was already attached to the MainCamera, each time I click the the script in the Inspector, 2 or 3 NullReferenceExceptions get added in the Console.

What am I doing wrong?

using UnityEngine;
using System.Collections;

public class CalculateStats : MonoBehaviour {

    private string _Name;
    private int _Experience;
    private int _Level;

    public string Name
    {
        get{return _Name;}
        set{_Name = value;}
    }
    public int Experience
    {
        get{return _Experience;}
        set{_Experience = 200;}
    }
    public int Level
    {
        get{return _Level;}
        set{
            _Level = _Experience/1000;
        }
    }

}

using UnityEngine;
using UnityEditor;
using System.Collections;

[CustomEditor(typeof(CalculateStats))]
public class CalculateStatsEditor : Editor {

    public override void OnInspectorGUI()
    {

        CalculateStats calcStat = (CalculateStats)target;

        EditorGUILayout.LabelField("Player Name", calcStat.Name.ToString ());

    }

}
2

Ok I’ve fixed the problem. Line 6 in CalculateStats.cs should be

private string _Name = "";