Heroku: ERROR SyntaxError: Unexpected end of JSON input

ERROR:

 ERROR SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at Response.Body.json 

---

LIVE:

https://voting-app-10.herokuapp.com/polls

---

QUESTION:

When I try to create a poll locally, everything works fine.

When deployed to heroku I get the error above.

What could be causing this ?

---

CODE:

Here is the project code: https://www.dropbox.com/s/6eop089d2dehm7p/Voting%20App.zip?dl=0

---

poll.service

addPoll(poll: Poll) {
        const body = JSON.stringify(poll);
        const token = localStorage.getItem('token')
            ? '?token=' + localStorage.getItem('token')
            : '';
        const headers = new Headers({
          'Content-Type': 'application/json',
          'Authorization': 'Bearer ' + token
        });
        return this.http.post('https://voting-app-10.herokuapp.com/poll', body, {headers: headers})
            .map((response: Response) => {
                const result = response.json();
                const poll = new Poll(
                    result.obj.title,
                    result.obj.choice1,
                    result.obj.choice2,
                    0,
                    0,
                    result.obj.user.firstName,
                    result.obj._id,
                    result.obj.user._id,
                    );
                this.polls.unshift(poll);
                return poll;
            })
            .catch((error: Response) => {
                this.errorService.handleError(error.json());
                return Observable.throw(error);
            });
    }

routes/poll

router.post('/', function (req, res, next) {
    var decoded = jwt.decode(getToken(req));
    User.findById(decoded.user._id, function (err, user) {
        if (err) {
            return res.status(500).json({
                title: 'An error occurred',
                error: err
            });
        }
        var poll = new Poll({
            title: req.body.title,
            choice1: req.body.choice1,
            choice2: req.body.choice2,
            counter1: 0,
            counter2: 0,
            user: user
        });

        poll.save(function (err, result) {
            if (err) {
                console.log("ERROR: "+err);
                return res.status(500).json({
                    title: 'An error occurred',
                    error: err
                });
            }
            user.polls.push(result);
            user.save();
            res.status(201).json({
                poll: 'Saved poll',
                obj: result
            });
        });
    });
});

via Coder1000