[refresh] undefined method 'model_name' when no posts exist and accessing admin section

[mindscratch]

I installed a fresh clone of the refresh branch and so I had no posts. When I accessed the admin section I got a "undefined method" error. Turns out the posts_controller#new method sets "@post" equal to a post that it looks up or to "Post.first". However, if you have no posts the view fails to render.

[natew]

We need some testing definitely, would be much appreciated if you could investigate!