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)
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?