Fix for sidebar bug on index page

Simple fix for #1869 .

Currently it would remember the last position (expanded or collapsed) which is fine while browsing the docs, but it creates a problem on the home page, as it uses no sidebar button
and i.e can't be re-expanded.

This is a quick fix that works fine.. I've added a comment to serve as a futre-TODO to make it still use cookies while not affecting the main page. right now I don't have time for that.

But this works for now :)