In case you don’t use steam, find your app-1.10.0 folder, make sure there is an app-1.9.4 folder next to it and then move the app-1.10.0 folder somewhere else. I would suggest to back it up as you never know…and you should be up running again for now.
In case you do use steam, there are a lot of threads with solutions. I don’t use steam, so i can not evaluate them.