Opening pulldash from the files tab gives a blank screen

# Steps to reproduce
1. Go to a PR on Github and open the files tab (i.e. `https://github.com/coder/pulldash/pull/4/files`)
2. Rename `github.com` to `pulldash.com` (i.e. `https://pulldash.com/coder/pulldash/pull/4/files`)
3. See a blank screen and `No routes matched location "/coder/pulldash/pull/4/files"` in the console

# Expected behaviour
A user visible error or automatic stripping of the url of tab components