Fix two issues where StandardPageView assumes it will always have access to a user

Summary: If we hit an exception very early, the request may not have a user yet. Don't assume it will.

Test Plan: Broke MySQL config on purpose to test some stuff, loaded Phabricator, got a nice error page instead of a super-fatal one.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7286