Code review comment for lp:~rockstar/launchpad/bug-517266

Hi Aaron-

  So, this is a change to the popupdiff info on the bugs page. Basically, if
the diff has no lines of difference, there won't be a node for 'a.diff-link'.
In those cases, we have nothing to highlight or attach events to.

  I don't think we can test this other than actually walking through it by
hand. Windmill doesn't have a way to say "There aren't any errors in the
browser, right?"

Cheers,
Paul