imap: Don't crash if mailbox UIDVALIDITY is zero when SELECTing a mailbox.
imap: Don't crash if mailbox UIDVALIDITY is zero when SELECTing a mailbox.

LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot