Fix some attachments not showing up

[leolost2605]

Fix some attachments not showing up.

Tries to fix #957

Only for reference if this doesn't work: the evolution way of getting whether a part is an attachment is (I think) found here

[leolost2605]

@wout could you maybe test whether this fixes your issue?
Unfortunately I currently don't have any attachments that don't load

[wout]

I'll try to test this asap, I'm swamped at the moment. I've sent you the email in question, maybe it helps to test the issue?

[leolost2605]

I'll try to test this asap, I'm swamped at the moment

No worries, test when you've got enough time :)

I've sent you the email in question, maybe it helps to test the issue?

Unfortunately the attachment didn't come along probably for the same reason it doesn't show up for you :(

[wout]

Okay, I've forwarded you the mail from Mailspring. In Mail, the attachment icon is present at the top left of the email, but the attachment is not visible at the bottom of the mail.

[leolost2605]

Unfortunately the attachment showed up in master and this branch for me, maybe Mailspring changed the format or something... 🤷

[leolost2605]

Maybe we can just merge this because I don't think it will introduce any regression but it might fix the problem 🤷

[danirabbit]

I can confirm attachments still show up here so