You are locked out until the developers release an updated for the new operating system. That's the way OSX apps work. I've seen other users with this issue as well. I suggest you wait until the developers will release a patch or a simple update. Leave anything untouched because if you tamper with the files, the software might not recognize them.
There is really nothing you can do at the moment except waiting. This is the website that you have to visit once in a while to see if they post new updates for SafeWallet.