ZF-12496: Zend_Validate_Identical don't launches if form element value is empty
Assume we have two form fields: password and password_repeat. Both of it is not required. The last one has attached Zend_Validate_Identical validator (token parameter points to password form field). In case when values (password:'12345',password_repeat:'1') passed - anything works great. But if to pass (password:'12345',password_repeat:'') form has success validation. It looks like since password_repeat form element has no any data submitted no any validation launches at all. I am not sure if it is exactly Zend_Validation_Identical class bug against Zend_Form::isValid mechanism. Anyway, '' is not identical to '12345', thus form shouldn't be validated successfully.