Just including code for you too, but privately...
The code works fine and sends emails, but I did initially try to have an upload file field so I could send an attachment however the attachments didn't come through as attached files via email when I've used the block email template.
I have tried to add the Send Email function numerous times and basically decided to delete the email folder from the webassist folder just to get back to a clean starting point again. I expected to not see the error messages again once I decided to no longer send attachments, but they're still appearing.
It's not causing me issues by the look of it, but I thought I'd share with you, just in case.