Don't break when trying to check if TemplateHooks apply on 404s.

On 404 pages, the request doesn't have a resolver_match. For TemplateHooks
that apply to base.html (like the base-css hook point, for example), this
was problematic because 404.html extends base.html, and so any TemplateHook
that injects itself in a base hook point on only certain pages would cause
breakages since the resolver_match couldn't be checked to see if the
TemplateHook should actually apply.

Reviewed at https://reviews.reviewboard.org/r/6035/.
Speed up the modalbox background fade, and make it darker.

This reduces the time of the modalbox background by more than half,
and makes the background darker. This helps to make things feel faster
when popping up a modalbox, and helps the modalbox to stand out better.

Reviewed at https://reviews.reviewboard.org/r/6149/