R1:7274e4857c23

Fix a bug where Phortune could fatal while building crumbs

Summary: Ref T12451. `$this->getAccount()` may not return an account.

Test Plan:
- Visit `/phortune/X/`, where `X` is the ID of an account you don't have permission to view.
- Before patch: fatal.
- After patch: normal policy exception page.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12451

Differential Revision: https://secure.phabricator.com/D17689