bcachefs: Fix warning in bch2_fs_journal_stop()

j->last_empty_seq needs to match j->seq when the journal is empty

Reported-by: [e-mail]
Signed-off-by: Kent Overstreet <[e-mail]>

fs/bcachefs/journal.c

···
 	}
 
 	if (!had_entries)
-		j->last_empty_seq = cur_seq;
+		j->last_empty_seq = cur_seq - 1; /* to match j->seq */
 
 	spin_lock(&j->lock);