There are several ways to clean up empty objects. Look around this forum and you will find some relevant questions from other users.
Search results are based on what you enter to look for. On empty object and empty record I finally found some posts that deal with the subject. Filtering seems to be the way to go, eventually with a garbage collector than runs periodically. But this makes my application patchwork.
Users do things that you would not expect, and navigating away from a new-form is one of them. This should be handled by the core (Mendix) and not by the developers creating filters and adding attributes to each form and entity to make it full-proof and fool-proof.
FYI, two posts that I found helpful - https://forum.mendix.com/questions/1890/Handling-empty-and-useless-objects - https://forum.mendix.com/questions/2043/Empty-Records-Handling