Over the last couple of weeks a lot of XBMC repositories have been empty making it impossible to install XBMC addons through those repositories. During the last couple of weeks the website GitHub has been experiencing problems which is where a lot of those Repositories are hosted. The problems are said to be due to an attack on their servers. They are in the process of fixing it and should have everything back to normal soon. Until then, we will just need to hang tight until everything is fixed.