pop3-migration: "first POP3 msg" warning didn't actually show the fir…

…st one.

It was showing the first index in an array, which had nothing to do with
being the first POP3 message number.

src/plugins/pop3-migration/pop3-migration-plugin.c

@@ -605,7 +605,7 @@ pop3_uidl_assign_by_hdr_hash(struct mailbox *box, struct mailbox *pop3_box)
 	struct imap_msg_map *imap_map;
 	unsigned int pop3_idx, imap_idx, pop3_count, imap_count;
 	unsigned int first_seq, missing_uids_count;
-	uint32_t first_missing_idx = (uint32_t)-1;
+	uint32_t first_missing_idx = 0, first_missing_seq = (uint32_t)-1;
 	int ret;
 
 	first_seq = mbox->first_unfound_idx+1;
@@ -653,8 +653,11 @@ pop3_uidl_assign_by_hdr_hash(struct mailbox *box, struct mailbox *pop3_box)
 		} else if (!pop3_map[pop3_idx].common.hdr_sha1_set) {
 			/* we treated this mail as expunged - ignore */
 		} else {
-			if (first_missing_idx == (uint32_t)-1)
+			uint32_t seq = pop3_map[pop3_idx].pop3_seq;
+			if (first_missing_seq > seq) {
+				first_missing_seq = seq;
 				first_missing_idx = pop3_idx;
+			}
 			missing_uids_count++;
 		}
 	}
@@ -663,8 +666,7 @@ pop3_uidl_assign_by_hdr_hash(struct mailbox *box, struct mailbox *pop3_box)
 
 		str_printfa(str, "pop3_migration: %u POP3 messages have no "
 			    "matching IMAP messages (first POP3 msg %u UIDL %s)",
-			    missing_uids_count,
-			    pop3_map[first_missing_idx].pop3_seq,
+			    missing_uids_count, first_missing_seq,
 			    pop3_map[first_missing_idx].pop3_uidl);
 		if (imap_count + missing_uids_count == pop3_count) {
 			str_append(str, " - all IMAP messages were found "