Correct the generation of "<th />" IDs on left-hand-side of image changesets
Summary:
Fixes T7682. The left-hand-side "<th />" row did not generate with the correct ID.
(I couldn't reproduce the exact issue described in T7682, but hovering comments on either side now works properly for me.)
Test Plan:
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T7682
Differential Revision: https://secure.phabricator.com/D17926