wallet: only log broken if we have duplicate scids in channels.

This was reported, but the channel was closed.  So however we ended
up with a duplicate, we're no *worse* off than we were before migration?

Fixes: ElementsProject#5760
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

wallet/db.c

@@ -1486,6 +1486,7 @@ static void migrate_channels_scids_as_integers(struct lightningd *ld,
 {
 	struct db_stmt *stmt;
 	char **scids = tal_arr(tmpctx, char *, 0);
+	size_t changes;
 
 	stmt = db_prepare_v2(db, SQL("SELECT short_channel_id FROM channels"));
 	db_query_prepared(stmt);
@@ -1497,6 +1498,7 @@ static void migrate_channels_scids_as_integers(struct lightningd *ld,
 	}
 	tal_free(stmt);
 
+	changes = 0;
 	for (size_t i = 0; i < tal_count(scids); i++) {
 		struct short_channel_id scid;
 		if (!short_channel_id_from_str(scids[i], strlen(scids[i]), &scid))
@@ -1509,12 +1511,21 @@ static void migrate_channels_scids_as_integers(struct lightningd *ld,
 		db_bind_scid(stmt, 0, &scid);
 		db_bind_text(stmt, 1, scids[i]);
 		db_exec_prepared_v2(stmt);
+
+		/* This was reported to happen with an (old, closed) channel: that we'd have
+		 * more than one change here!  That's weird, but just log about it. */
 		if (db_count_changes(stmt) != 1)
-			db_fatal("Converting channels.short_channel_id '%s' gave %zu changes != 1?",
-				 scids[i], db_count_changes(stmt));
+			log_broken(ld->log,
+				   "migrate_channels_scids_as_integers: converting channels.short_channel_id '%s' gave %zu changes != 1!",
+				   scids[i], db_count_changes(stmt));
+		changes += db_count_changes(stmt);
 		tal_free(stmt);
 	}
 
+	if (changes != tal_count(scids))
+		fatal("migrate_channels_scids_as_integers: only converted %zu of %zu scids!",
+		      changes, tal_count(scids));
+
 	/* FIXME: We cannot use ->delete_columns to remove
 	 * short_channel_id, as other tables reference the channels
 	 * (and sqlite3 has them referencing a now-deleted table!).