Returning server error Jade not finding isLoggedIn undefined

I'm building a web app with Node.js, mongodb, express and jade. When I start the server all is well on the terminal but when I load the webpage it returns a server error regarding a jade template...can you help?

error at /
{ [TypeError: /Users/Web/views/layout.jade:11
9|     section.login
10|       ul
>11|         if session.isLoggedIn
12|           li
13|             a(href="/logout") Logout
14|         else

Cannot read property 'isLoggedIn' of undefined]

Looking at my code on the layout.jade and login.js where I have all the codeI can't find the error. And this is following the exact structure and code of a course I recently followed.

layout.jade

html5
html
  head
   title= pageTitle
body
  header
    h1= pageTitle
  a(href="/") Home
  section.login
   ul
    if session.isLoggedIn
      li
        a(href="/logout") Logout
    else
      li
        a(href="/login") Login
      li
        a(href="/signup") Create Account
section.content
  block content

login.js

var mongoose = require('mongoose');
var Member = mongoose.model('Member');

var cleanString = require('../helpers/cleanString');
var hash = require('../helpers/hash');
var crypto = require('crypto');

module.exports = function (app) {

  app.get('/signup', function (req, res) {
    res.render('signup.jade');
});

// create a new account
app.post('/signup', function(req, res, next) {
    var email = cleanString(req.param('email'));
    var pass = cleanString(req.param('pass'));
    if (!(email && pass)) {
        return invalid();
    }

    Member.findById(email, function (err, member) {
        if (err) return next(err);

        if (member) {
            return res.render('signup.jade', { exists: true });
        }

        crypto.randomBytes(16, function (err, bytes) {
            if (err) return next(err);

            var member = { _id: email };
            member.salt = bytes.toString('utf8');
            member.hash = hash(pass, member.salt);

            Member.create(member, function (err, newMember) {
                if (err) {
                    if (err instanceof mongoose.Error.ValidationError) {
                        return invalid();
                    }
                    return next(err);
                }

                //member created successfully
                req.session.isLoggedIn = true;
                req.session.member = email;
                controle.log('created member: %s', email);
                return res.redirect('/');
            });
        });
    });

    function invalid() {
        return res.render('signup.jade', { invalid: true});
    }
});
}