We have an escape hatch that allows users to type in a review request ID into

the search box and jump straight there. Unfortunately, the way that it was

implemented meant that if there were no results for that (say, a user was

typing in a bug number instead), it would crash.
It turns out that we already had code that handled looking up the review

request ID directly. I've added some additional permissions checking to that to

make us only redirect when the searching user has access to the review request,

and otherwise the search is done using the text rather than trying to have

special cases for digit searches vs. non-digit searches.

Ran unit tests.
Searched for a string of digits that did not correspond to a review request

  ID.