Content area always sized as if both sidebars active.

Whist upgrading one of my sites from D6 to D7, I noticed the main content area (#wrap_center) was not sizing properly.
The CSS was being applied as though both sidebars were active. A bit of testing revealed that the class ".both_sides" was being applied to the body element, regardless of whether the left, right, or no sidebars were used.
I eventually traced the problem to where the body element is printed in the html.tpl.php template. Although the get_sidebar_state() function seems to work correctly elsewhere, in html.tpl.php $page['sidebar_first'] always evaluates to true (the same goes for 'sidebar_last' and 'right_dark').

I have attached a patch file which fixes this error.
The patch removes the extra classes from the body element in the html.tpl.php file and adds the admire_grunge_preprocess_html() function to the template.php.
The preprocess function adds the 'mainbody' and the correct sidebar state class to the classes_array variable to be expanded when the body is rendered.

I hope this is useful to somebody. Although there doesn't seem to be much activity around this project.