Assertion failed: NULL != GeneratedClass ERROR

While packaging my game for Windows 64-bit, I encountered an error I was unable to find by its name on the Internet, so I decided to take it here.
I have no idea what caused the error, searching the log for summary has proven unsuccessful.
I have attached the log.

Thanks for your help!

You have some kind of NULL object that is trying to load textures; Probably some artifact from renaming/deleting things. Try to clean up your file / asset structure.