Don't crash if CLOSEing without open mailbox.
Don't crash if CLOSEing without open mailbox.

damoxc/dovecot,Distrotech/dovecot,LTD-Beget/dovecot,damoxc/dovecot,Distrotech/dovecot,LTD-Beget/dovecot,Distrotech/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,damoxc/dovecot,damoxc/dovecot,damoxc/dovecot,Distrotech/dovecot,Distrotech/dovecot,LTD-Beget/dovecot