More problems with get-new-mail in virtual IMAP folders

[Uday Reddy]

Doing a get-new-mail in the virtual folder of an IMAP folder generated this trace, with a BAD imap command issued:

VM FETCH 4520:4521 (BODY.PEEK[HEADER])
* 4520 FETCH (BODY[HEADER] {3938}
)
* 4521 FETCH (BODY[HEADER] {740}
)
VM OK Fetch completed.
VM NOOP
VM OK NOOP completed.
VM UID FETCH nil:nil (RFC822.SIZE)
VM BAD Error in IMAP command UID: Invalid UID messageset
VM LOGOUT
* BYE Logging out

And, this somehow caused sorting/threading to fail?

Retrieving new messages...
Updating summary...
Generating summary... 0
Sorting messages... done
Generating summary... 800
4483 messages, 2 new, 351 unread, 0 deleted
IMAP error: server said BAD
4483 messages, 2 new, 351 unread, 0 deleted
Generating summary... 0
vm-sort-messages: Unknown key: activiity