c# - nested custom list in custom list without passing

Question

pretty new to programing tackling on everything I can however finally hit a bump. Right to it, I'm trying to attach abilities to my hero so I can serialize easier. However whenever I try to add it says

NullReferenceException: Object reference not set to an instance of an object LevelUp.Update () (at Assets/LevelUp.cs:62) and does not add the test ability. so heres the script

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

    [System.Serializable]
    public class Hero
    {
         public string heroname;
         public List<Ability> heroability = new List<Ability>;

         public Hero(string name)
         {
              heroname = name;
         {

ability class

[System.Serializable]
public class Ability
{
    public string abilityname;
    public float abilitydmg;

    public Ability(string name, float damage)
    {
        abilityname = name;
        abilitydmg = damage;
    }
}

and then adding outside on a void update (gameobject is set with holder)

public class LevelUp : MonoBehaviour {
    public GameObject heroOne;
    public Hero hero1;
    public Ability a1;
    public List<Ability> test = new List<Ability>();

    void Update()
    {    
        hero1 = heroOne.GetComponent<FirstHolder>().hero1;
        hero1.heroability.Add(new Ability("test", 1));
    }

and this is where the error is coming from. any insight would be appreciated. Thank you!