[Inkscape-devel] Strange behaviour, not existing items

Hi, I'm taking a look at a drawing Kees Cook mentioned some months ago: http://www.wherearewe.co.nz/svg/world.svgz I was trying to clean it up a little and I found that when I ungroup some of the groups they split up in a group of 4 objects, when I ungroup that group I get one figure and 3 invisible objects. I tried to change the colours, but it doesnt affect them. When I click the "Adjust selection to window" button it zoom out very much so I only see the complete drawing very small. What are these "invisible" things?

Thank you,