make sure that path is a String

Someone is trying to get this page:
`/include.php?path[docroot]=http://www.google.com/humans.txt?`

This obviously doesn't work; and shouldn't work; but it also should not crash the process IMO. The reason that our code fails is that the stupid script that looks for a relay found the way to make Rails make the path variable into a Hash.

It's really silly, but it prevents a flood of errors in Errbit.