Hide delete button from non-owners

It may have something to do with my commentable resource being a nested one (I had to modify the controller a good bit to get it working with a somewhat weird routing scheme), but with a nested commentable, I was always seeing delete buttons in the view, for all comments, regardless of what user I was logged in as.

I think this should safely hide the delete button from non-owners without hurting any other logic, and do so with just two lines of code.  Let me know what you think.