If title is edited after posting, email link goes to not found

If someone edits their topic after posting it, clicking on the notification email doesn't show the page. It says not found. I usually have to find the user, and find the discussion they were talking about.

I originally thought it was because they were getting deleted for some reason, but most of the time, its because they edit the title, which changes the URL, so the link goes to the old url, not the new one.

This could be fixed by making a redirect from the old url if the post is edited.