once you fixed the problem you of course commit the change to the code on disk. there is nothing in the workflow that prevents you from doing that. you are not going to just fix apps in production without running your tests and what not. at worst you fix an error in a production system, and run the tests afterwards to make sure everything is clean. but mostly this feature is used during development when your code is still incomplete. not having to restart every time there is an error simply speeds up your development loop.