Rustdoc: faulty search index entry

STR:
- Open the [std docs](http://doc.rust-lang.org/nightly/std/)
- Search for "-"
- Open the first [search result](http://doc.rust-lang.org/nightly/std//index.html)

I expected either to not get a search result for the crate root or a correct URL.

Instead the search result yields a badly rendered version of the crates index page.
(note the double slash before `index.html` in the URL)
