There's a lot of forums out there were you can't delete your own posts, even if there's nothing below it. So when you accidentally double post, all you can do is that.
You might want to check the dates on the posts, though, commander. Some boards here aren't too high traffic, so there are a few topics somewhat near the top that are a bit too old to post in without something to add to the original topic. Don't worry about it this post too much, though. Just keep it in mind.