mail sent from identity without display name gets displayname 'null' for messages saved as draft

Checklist

• I have used the search function to see if someone else has already submitted the same bug report.
• I will describe the problem with as much detail as possible.

App version

6.602 as well as 6.707

Where did you get the app from?

F-Droid

Android version

11 (LineageOS 18.1)

Device model

Samsung GT-I9301I

Steps to reproduce

1. Create an Identity with your email address as sender and leave the "Your Name" field empty.
2. Compose a new Email (to yourself), select the identity just created and save this message as draft.
3. Re-Open this draft from the drafts folder and send it.

Expected behavior

The email is sent with From: myaddress@example.com in its headers.

Actual behavior

The From header of the sent mail is set to From: null <myaddress@example.com>.

Side-note: This malfunction even causes some mail providers' spam filters to increase the spam score for such mails (observed for Posteo).

Logs

Uploaded log file (captured via adb) here: k-9-log.txt

Reproduce the issue by creating an identity without a name, saving a draft, reopening it, and sending it. Trace the draft reopen and send flow to find where the From header is assembled; done means the sent header contains only the email address when no display name was provided.