Site won't redirect after submitting form

<?php

require __DIR__ . '/vendor/autoload.php';

date_default_timezone_set ('Europe/London');

use Monolog\Logger;
use Monolog\Handler\StreamHandler;

//$log = new Monolog\Logger('name');
//$log->pushHandler(new Monolog\Handler\StreamHandler('app.txt', Monolog\Logger::WARNING));
//$log->addWarning('Warning');

$app = new \Slim\Slim(array(
    'view' => new \Slim\Views\Twig()
));

$view = $app->view();
$view->parserOptions = array(
    'debug' => true
);

$view->parserExtensions = array(
    new \Slim\Views\TwigExtension(),
);

$app->get('/', function() use($app){
  $app->render('index.twig');
})->name('home');

$app->get('/contact', function() use($app){
  $app->render('contact.twig');
})->name('contact');;

$app->post('/contact', function() use($app){
  $name = $app->request->post('name');
  $email = $app->request->post('email');
  $msg = $app->request->post('msg');

  if(!empty($name) && !empty($email) && !empty($msg)) {
    $cleanName = filter_var($name, FILTER_SANITIZE_STRING);
    $cleanEmail = filter_var($email, FILTER_SANITIZE_EMAIL);
    $cleanMsg = filter_var($msg, FILTER_SANITIZE_STRING);
  } else {
    //message the user that there was a problem
    $app->redirect('/contact');
  }

  $transport = swift_SendmailTransport::newInstance('/usr/sbin/sendmail -bs');
  $mailer = \Swift_Mailer::newInstance($transport);

  $message = \Swift_Message::newInstance();
  $message->setSubject('Email from our website');
  $message->setFrom(array($cleanEmail => $cleanName));

  $message->setTo(array('treehouse@localhost'));
  $message->setBody($cleanMsg);

  $result = $mailer->send($message);

  if($result > 0) {
    // send thank you message
    $app->redirect('/');

  } else {
    // send a message to the user that the message failed ot send
    // log the error
    $app->redirect('/contact');
  }

});

$app->run();