js email validation freeze browser

Steps to reproduce:

``` php
$form = new Form;
$form->addText('email', 'Email:')
  ->addRule(Form::FILLED, 'Zadejte email')
  ->addRule(Form::EMAIL, 'Email nemá správný formát');
$form->addSubmit('send', 'Odeslat');
$this->template->form = $form;
```

paste to input, click to submit:
`"><img src=x onerror=prompt(document.domain)>`

result: 
freeze browser tab
