Due to me accidentally closing butler process early, I now have a blank build in build history that has "Started" status on it stuck. I have uploaded a new build through butler, so the "started" build is now pre-last version in build history. Is this anything to worry about? It's not going to cause any database problem?

You should be able to push again and it will base the patch off the most recent completed build. If you run into any issues be sure to tell us.

Yea, seems to be nothing to worry about as gamedev and player. Alright! Just hope such hanging(?) builds are no problem to your side.