Fixed admin 404 page broken image refrence

The little ghost image tag was broken on the admin 404 page, resulting in the screenshot below. It was missing a double quote on the `src` attribute! This adds it back in.

![screen shot 2013-12-12 at 20 43 47](https://f.cloud.github.com/assets/390392/1737188/c3a0301e-636e-11e3-9292-c041a17b8afa.png)