Comment and Batch Comment forms, cannot send public comment without email recipients

[kaladay]

Filling out the Comment (or the Batch Comment) forms.
With "Public" radio selected.

The "Add Email Recipients" is a checkbox and can be disabled.
However, when it is disabled, it is no longer possible to submit the comment.

Either this should not be a checkbox and e-mails are always required to be sent, or when the checkbox is unchecked allow submitting the comment without any emails.