If you have the same error as him, try loading other saves! Not all of them will work. Saves you made after major scene transitions are more likely to load succesfully.
You should've kept more saves. It's common that a few of them will break when you update the game.
If you don't want to start over then install my mod and press the N of eterNum on the main menu 5 times to start from a chapter of your choice. If you then want to play without guidance you can disable my mod in the settings.
As a lesson for next time: Save often and in different slots! The best spots to save at are right after major scene transitions, those saves are most likely to survive game updates.