in a protected app in our dev environment, I created a resource query and then never selected a resource. I accidentally left this in when I committed my changes and then merged them into the main branch. This causes the automated deployment to fail. This caused some issues when trying to revert to the previous commit for some reason, although that may have been my fault. Committing a resource query without an associated resource should be blocked, or the deployment bot should be able to handle deploying it.
Thanks for flagging this, @aharmange! I like the idea of blocking the commit if we detect breaking changes, but that hinges on already knowing what constitutes a breaking change. 
You've discovered at least one of them!
I'll talk to our team here about how we might be able to implement this. At the very least, we can address this particular issue. I'll keep this topic updated as the conversation progresses!