fix expiration completion after external expunge

when the expiration is interrupted, but an external expunge removes the
near-side message before we resume, we would just drop the transaction,
resulting in an "unmarked" orphan.

a corner case is an expiration that finishes, but initially isn't
expunged (probably due to an interruption), followed by an unexpiration
that gets interrupted, and the message being expunged externally
(because it's still marked as deleted). we obviously can't complete
that transaction without re-propagating the message, so effectively
cancel it instead.

src/sync.c

@@ -1047,6 +1047,11 @@ box_loaded( int sts, message_t *msgs, int total_msgs, int recent_msgs, void *aux
 					// The target may be in an unknown state (not fetched).
 					if ((t == F) && (srec->status & (S_EXPIRE|S_EXPIRED))) {
 						/* Don't propagate deletion resulting from expiration. */
+						if (~srec->status & (S_EXPIRE | S_EXPIRED)) {
+							// An expiration was interrupted, but the message was expunged since.
+							srec->status |= S_EXPIRE | S_EXPIRED;  // Override failed unexpiration attempts.
+							JLOG( "~ %u %u %u", (srec->uid[F], srec->uid[N], srec->status), "forced expiration commit" );
+						}
 						JLOG( "> %u %u 0", (srec->uid[F], srec->uid[N]), "near side expired, orphaning far side" );
 						srec->uid[N] = 0;
 					} else {