R1:03e5d69817c9

Fix an error in Diffusion when the Owners application is uninstalled

Summary:
See <https://discourse.phabricator-community.org/t/undefined-view-when-owners-is-uninstalled/451>.

When Owners is not installed, Diffusion can fatal with a bad `$view`.

Test Plan:
- Uninstall Owners.
- View the content of any file in Diffusion.
- Before: fatal on `$view` undefined.
- After: Valid page with no owners information.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.