Arg - good catch. I had two '.rej' files (left over from a merge or update) in my directories, which svn didn't report when I checked It doesn't cause any crash, so it should be fine for a RC.
I should have mentioned it: delete the files Glass.stkskin.rej and Ocean.stkskin.rej in .../SuperTuxKart/data/gui/skins to confirm that this works for you.