Fix bug with mousein / mouseout event on comment preview at bottom of page

Summary: these comments aren't associated the same way with the actual changeset ui. ergo, don't update the reticle when mousing over these comments.

Test Plan: moused over comments at bottom - no more JS error. mouse over comments inline - reticle highlighting / de-highlighting still occurred as expected.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1657

Differential Revision: https://secure.phabricator.com/D3299