Don't create empty span if post has no tags

[Samasaur1]

https://github.com/Samasaur1/samasaur1.github.io/blob/9afc0a90061000bf1d65850d0f90eb488b605cd8/_includes/post.html#L6-L21

It should be as simple as moving the open/close span tags inside the Liquid if statement.