I created a form using the form factory which essentially contains only one field:

$builder = $this->container->get('form.factory')->createBuilder(
    'email', 
    $person->getEmail()
);

Trying to bind this form to the post triggers the following error:

Warning: array_replace_recursive() [function.array-replace-recursive]: Argument #1 is not an array in D:\workspace\09_061_Shifter_RAI\vendor\symfony\src\Symfony\Component\Form\Form.php line 583