So it's not just one blank file, you've got dozens of blank files.
It is baffling because I've never had it happen in 10 years of using A:M almost every day. Not even in the gazillion files I saved while working on TWO.
For now, turn off auto save, do only "Save As", never use "save", and every hour look at that directory to see if suddenly the file got smaller after a certain save.
Set a timer to remind you to do it.