Hi,

It is a bug, I just fixed it here so it will be fixed in the next releae.

The bug only occurs if the blog post does not have a friendly url. When you make a blog post, after you put the title when you tab out of that box it will auto suggest a friendly url based on the title. Usually this happens pretty fast but if you save the post before it happens then it can be saved without a friendly url.

You can fix the post by editing it again, it should suggest an url again so all you have to do is save again. 

Hope it helps,

Joe