title: CodeIgniter: form submitted with <enter> fails form validation
body: <p>I have this problem with CodeIgniter: 
  - when I click the submit button in a form, the form is submitted and validated correctly
  - when I don't click the submit button, just hit <code>&lt;enter&gt;</code>, the form validation always fails
  Any solution? Is that a flaw in CI's form validation or am I missing something?</p>
  
  <p>What code I have there:</p>
  
  <pre><code>--- the form view ---
  
  form_open("/");
  ...some inputs...
  echo form_submit('submit', 'Přihlásit');
  form_close();
  ...
  
  --- the controller ---
  
  $this-&gt;CI-&gt;load-&gt;helper('form');  
  $this-&gt;CI-&gt;load-&gt;library('form_validation');
  
  $this-&gt;CI-&gt;form_validation-&gt;set_rules('id_uziv', 'ID', 'required');   
  $this-&gt;CI-&gt;form_validation-&gt;set_rules('heslo', 'Heslo', 'required');  
  //... see, no rules have anyhting to do with the submit button
  
  if ($this-&gt;CI-&gt;form_validation-&gt;run() == FALSE) {
    // validation OK
  }
  else {
    // validation failed
  }
  </code></pre>