Fix draggability of the comment dialog.

Review Request #8384 — Created Sept. 5, 2016 and submitted — Latest diff uploaded

Information

Review Board
release-3.0.x
ab21aa6...

Reviewers

The new fancy stuff in the DnD uploader view was interfering with the drag
events used by the comment dialog. This change fixes it so we don't try to use
data that doesn't exist.

I could drag the dialog around again.