Description:
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When I have a first select option that don't have second select option, then the rule failed to validate and submit the form values to process.

Example
When I select 'Argentina' (below), that don't have second options (because still he was not inserted in the database) then the hierselect load the second select empty, then I submit the form and the validate failed and process the form.



Reproduce code:
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    $main[0] = "Brasil";
    $main[1] = "Argentina";
    
    $secondary[0][0] = "Porto Alegre";
    $secondary[0][1] = "Rio de Janeiro";
    
    $form->setDefaults(array('location'=>array(0,1)));
    $sel =& $form->addElement('hierselect', 'location', 'Location:');
    $sel->setMainOptions($main);
    $sel->setSecOptions($secondary);    
    $form->addElement('submit', 'btnSubmit', 'Submit');
    
    $form->addRule('location', 'Field Required', 'required');

    if ($form->validate())
        $form->process($function = 'insert', false);

    $form->display();

Expected result:
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I expect that the rule break and return the message 'Field Required' to second element location too