no email sent for zip files

Document orders for zip files are not receiving the email with the download link. All other file types work as expected.

• zip files are included in the list of allowed file types.
• we have disabled the send documents via email option. the email just includes the download link.
• neither the initial order email or "resend email" tool works
• the file itself is confirmed to be present in the documents folder

we sorted out the issue. the "Confirmation Email Subject (For Free Download)" and Body fields were empty. I'm not sure if they were missing a default value or what, but with no values in those fields, it does not send an email. You should improve validation and ensure an accurate message is returned if the email is not actually sent.

there's a second issue -- when you save the messages config form it redirects to an eventbooking URL. the problem is in controller/message.php -- there's a bad URL in the redirect. there is a second place where eventbooking is referenced -- in the paypal plugin. you should fix those.