title: Avoiding form validation enforced checks on non-required fields in CodeIgniter
body: <p>I have an e-mail field which is -not- required in my form validation. It should be able to be left blank. However, when I use the "valid_email" parameter of the form validation's set_rules, it still gives an error message that the e-mail is not valid when it's not supposed to check this if the field has not been filled out.</p>