Lucky both of us, actually! I got it (for now)...
Alright, all you need to do is go to where the game is installed and add two new folders - an empty "www" folder just next to the executable, then a folder named "save" inside that, and everything worked again on my end. The bug appeared when trying to write your options to a directory that didn't exist.
If I had to guess, it's because they would look like orphan folders to the app, and when it pulls and installs the executable it didn't seem to drop those in for me. That might be an itch app problem I can't solve, but I will absolutely put a warning on the top of the page here!