NullReferenceException: Object reference not set to an instance of an object when calling RPC

Hello! I am currently working on a small school project and ran into this issue. I can't for the life of me figure out where I went wrong. Some assistance would be much appreciated! Sorry in advance for the spaghetti. Still learning! :)

NullReferenceException: Object reference not set to an instance of an object
TeamManager.Set () (at Assets/Scripts/TeamManager/TeamManager.cs:77)
UnityEngine.Events.InvokableCall.Invoke () (at <e98ed0368295432e8c11e52d6243ee11>:0)
UnityEngine.Events.UnityEvent.Invoke () (at <e98ed0368295432e8c11e52d6243ee11>:0)
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using Photon.Pun;

public class TeamManager : MonoBehaviourPun
{
    public string houseSelected;
    public string teamSelected;
    public string ID;
    public bool ready;
    public int readyCount;

    [SerializeField] private Button glasheen;
    [SerializeField] private Button reed;
    [SerializeField] private Button daffey;
    [SerializeField] private Button fitzgerald;
    [SerializeField] private Button hider;
    [SerializeField] private Button seeker;
    [SerializeField] private Button set;

    PhotonView pv;

    List<TeamManager> teamUserData;

    Color original = new Color(250, 250, 250);
    private void Start()
    {
        teamUserData = new List<TeamManager>();
        pv = GetComponent<PhotonView>();
    }

    private void Update()
    {
        Debug.Log("ID: " + ID + " / House: " + houseSelected + " / Team: " + teamSelected + " / ready: " + ready);
        foreach (TeamManager a in teamUserData)
        {
            Debug.Log("ID: " + a.ID + " / House: " + a.houseSelected + " / Team: " + a.teamSelected + " / ready: " + a.ready);
        }
    }

    public TeamManager (string UserID, string house, string team, bool isReady)
    {
        ID = UserID;
        houseSelected = house;
        teamSelected = team;
        ready = isReady;
    }

    [PunRPC]
    void RoomReady(string sentID, string sentHouse, string sentTeam, bool ready)
    {
        UpdateTeamData(sentID, sentHouse, sentTeam, ready);
        SetReady(1);
    }

    void UpdateTeamData(string updateID, string updateHouse, string updateTeam, bool isReady)
    {
        teamUserData.Add(new TeamManager(updateID, updateHouse, updateTeam, isReady));
    }

    void SetReady(int num)
    {
        readyCount += num;

        if (readyCount == PhotonNetwork.CurrentRoom.MaxPlayers)
        {
            gameObject.SetActive(false);
        }
       
    }

    public void Set()
    {
        ready = true;
        pv.RPC("RoomReady", RpcTarget.AllViaServer, pv.Owner.UserId, houseSelected, teamSelected, true);
    }
   

    public void HouseSelect(string house)
    {
        houseSelected = house;

        HouseButtonCheck();
    }

    public void TeamSelect(string team)
    {
        teamSelected = team;

        TeamButtonCheck();
    }

    private void HouseButtonCheck()
    {
        ColorBlock colors;

        if (glasheen.name == houseSelected)
        {
            colors = glasheen.colors;
            colors.normalColor = glasheen.colors.highlightedColor;
            glasheen.colors = colors;
        }
        else
        {
            colors = glasheen.colors;
            colors.normalColor = original;
            glasheen.colors = colors;
        }

        if (reed.name == houseSelected)
        {
            colors = reed.colors;
            colors.normalColor = reed.colors.highlightedColor;
            reed.colors = colors;
        }
        else
        {
            colors = reed.colors;
            colors.normalColor = original;
            reed.colors = colors;
        }

        if (daffey.name == houseSelected)
        {
            colors = daffey.colors;
            colors.normalColor = daffey.colors.highlightedColor;
            daffey.colors = colors;
        }
        else
        {
            colors = daffey.colors;
            colors.normalColor = original;
            daffey.colors = colors;
        }

        if (fitzgerald.name == houseSelected)
        {
            colors = fitzgerald.colors;
            colors.normalColor = fitzgerald.colors.highlightedColor;
            fitzgerald.colors = colors;
        }
        else
        {
            colors = fitzgerald.colors;
            colors.normalColor = original;
            fitzgerald.colors = colors;
        }
    }

    private void TeamButtonCheck()
    {
        ColorBlock colors;

        if (hider.name == teamSelected)
        {
            colors = hider.colors;
            colors.normalColor = hider.colors.highlightedColor;
            hider.colors = colors;
        }
        else
        {
            colors = hider.colors;
            colors.normalColor = original;
            hider.colors = colors;
        }

        if (seeker.name == teamSelected)
        {
            colors = seeker.colors;
            colors.normalColor = seeker.colors.highlightedColor;
            seeker.colors = colors;
        }
        else
        {
            colors = seeker.colors;
            colors.normalColor = original;
            seeker.colors = colors;
        }
    }
}