notmuch vim failing to show rfc822 attachments

[Kay]

Dear notmuchers,

I've recently switched to using notmuch for mail management and I like
it so far. The only thing stopping me from full joy is that neither alot
nor the notmuch vim frontend can display message/rfc822 attachments.

When I open the mails containing rfc822 attachments in alot, their
content is shown, but their metadata is lost. When I try to open the
messages in the notmuch vim frontend, I get the following error

Error detected while processing function
<SNR>20_search_show_thread[10]..<SNR>20_show:
line   39:
NoMethodError: undefined method `mime_type' for nil:NilClass

After pressing enter thereafter, I see the mail but none of the rfc822
attachments. Mutt shows the attachments plus their headers flawlessly.

I'm using the current notmuch-vim version I pulled today alongside
notmuch 0.21. I tested the same thing using notmuch and alot with
current packages in the Arch repositories of both and alot did not
show the message headers, as mentioned above.

Thank you in advance,
Kay