Don't crash if client disconnects in the middle of APPEND.
Don't crash if client disconnects in the middle of APPEND.

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