New mails in read only mode are displayed nicely now: T7843: GpgOL: Empty OpenPGP mails with "Read as plain" activated.
Old mails still have some of the old issues. With the fix above, opening an old mail with many/big mail attachments often (not always) results in a partially unresponsive interface, resizing the window will result in "Outlook (Not Responding)":
- e.g. ted:INBOX/Mailformate/0002 openpgp both text mails
- with read as plain
- without read as plain
This might hint at some underlying problem, which might occur in certain circumstances, so this should better be investigated.
Split from T7843: GpgOL: Empty OpenPGP mails with "Read as plain" activated

