This has also just happened to me when I upgraded from app version 23 to app version 25 (on Linux - I had to uninstall and remove the old repository)... the new version still has all my games in the directory along with details about them but the file that contains the list of games I have is empty - none of my games were paid for but I don't want to have to download them all again :( - thaqt took a loooooong time :(