Understood, but I've not ever seen an email come through with an empty text part, it's always missing and there's an HTML part.

Even if it did come through, that wouldn't be useful, so if anything we should handle it and pass through.

I'm thinking that on [this line](https://github.com/thoughtbot/griddler/blob/master/lib/griddler/email.rb#L19) we should do `text.presence || html`.