TypeError: Cannot read properties of null (reading 'get') in Next.js and Mongoose application

I'm making an ecommerce application with nextjs and mongoose and a jwt token in a cookie.

I have the following error : TypeError: Cannot read properties of null (reading 'get')

models/order.js :

import {model, models, Schema} from "mongoose";
import mongoose from 'mongoose';

const OrderSchema = new mongoose.Schema({
  products: {
    type: Object,
    required: true,
  },
  user_id: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "User",
  },
  name: {
    type: String,
    required: true,
  },
  email: {
    type: String,
    required: true,
  },
  address: {
    type: String,
    required: true,
  },
  city: {
    type: String,
    required: true,
  },
  paid: {
    type: Number,
    default: 0
  },
}, {timestamps: true});

const Order = models?.Order || model('Order', OrderSchema)

export default Order;

This error comes when I want to access my orders page (pages/orders.js) :

import { useEffect, useState } from "react";
import axios from "axios";
import jwt from "jsonwebtoken";
import cookie from "cookie";
import Order from "../models/Order";

function Orders() {
  const [orders, setOrders] = useState([]);
  

  useEffect(() => {
    async function fetchOrders() {
      const res = await axios.get("/api/secret");
      const secret = res.data.secret;
      // Get the JWT token from the cookies
      const token = cookie.parse(document.cookie).OursiteJWT;
      const decoded = jwt.verify(token, secret);
      const userId = decoded._id
      console.log(userId)
      // Fetch the orders for the user from the backend API
      const response = await axios.get(`/api/orders?user_id=${userId}`);
      const orders = response.data;

      setOrders(orders);
    }

    fetchOrders();
  }, []);

  return (
    <div>
      {orders.map((order) => (
        <div key={order._id}>
          <h2>Commande {order._id}</h2>
          <p>Utilisateur: {order.name}</p>
          <p>Adresse: {order.address}</p>
          <p>Ville: {order.city}</p>
          <p>Produits:</p>
          <ul>
            {order.products.map((product) => (
              <li key={product._id}>{product.name}</li>
            ))}
          </ul>
        </div>
      ))}
    </div>
  );
}

export default Orders;

I noticed that I can't put console.log in my useffect or in api calls that are in my useffect because my useffect doesn't even run because the problem comes from my model.
If I delete my useffect I still have the same error so the problem does not come from my useffect.

mongoose is server-side package. you cannot use the Order model inside client components. You can use models with server-side code, inside api functions or getServerSide functions.