WordPress 5.3 update causes media library file upload to break – Cannot convert undefined or null to object

So after updating to WP 5.3 I can no longer use the file upload to choose files to add. I get the following error:

Uncaught TypeError: Cannot convert undefined or null to object
    at g.cleanup (backbone.min.js:1)

Error in console:

How it shows when I try to choose an image:

I have the Classic Editor plugin installed so I can use it the classic way. I have disabled all other unnecessary plugins but the problem still persists. It’s only happened since the new WP core update to 5.3 yesterday.

Any ideas what’s going on here?

I had the same problem. In my case it was the Enhanced Media Library plugin, which looks as though it has not been updated in some time. I deactivated it, and all is good.