Hide Pager border if no pager exists

Summary: I guess we have this magical method that tells me if a pager is coming down the render pipe. Huzzah.

Test Plan: Test Branches page in Diffusion, see no pager border.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D18202