Fix not working 'Hide Whitespace changes' toggle.

The 'Hide Whitespace changes' toggle does not work on multiple browsers:
Chrome/Firefox/Opera.

Clicking the toggle for a diff with whitespace changes should dim references to
the whitespace changes and stop highlighting the changes. Instead the button
does nothing and a javascript error is thrown: Uncaught Error: Syntax error,
unrecognized expression: ol.index a[href=#5.2]

Testing done:
Uploaded a diff with whitespace changes and modified the jquery selector for the
changes references inside Chrome's developer tool.

Fixes bug 2885.
Reviewed at http://reviews.reviewboard.org/r/3832/