SelectBox: submitting with invalid value invalidates Form

When SelectBox is submitted and selected value isn't among specified values (e.g. someone tries to fix the form by editing it in FireBug or new application version was deployed before user send a form) the form is marked as invalid.

More info [CZ]: http://forum.nette.org/cs/11861-forms-controls-selectbox-by-nemel-vracet-null