root attributes aren't properly rendered

Reporting this against Lucid since it should still be supported and we're having a problem with it on the render farm for Wikimedia Commons.

See https://commons.wikimedia.org/wiki/File:Sulfamerazin.svg -- the thumbnails from 5 June 2010 show the how the SVG files as they render with after the upgrade to librsvg which resulted in User:Rillke coming back a year and a half later (shortly after the upgrade to Lucid) and updating the svg file to remove the dependency on the "stroke" attribute in the root element.

I tested this file against 2.35.1-0ubuntu1 backported to Lucid and found that the the newer version of rsvg worked properly.