When there is a new version of Logic Pro, it's a good time to back up your current version of the application, so you can revert back to an older version in cases of accessibility show stopper bugs or old projects not working right.
I demonstrate that its possible to back up your Logic Pro application, or that you can even keep multiple versions of Logic on your Mac at the same time. You can also follow this apple support article.
This tutorial shows you how to update Logic Pro before the App Store notifies you there is an update.
These methods should work for GarageBand as well. as a lot of other mac apps