after getting the error last night, I went back to v10 because I had some editing to do. I left the files in the editor (saved but not closed) that I was editing in the editor and exited it. When I restarted v10, the files were reopened (I like that).
When I started v11, it also reopened those files, and there was no error message. I then closed all of those files and exited the editor.
Upon restarting v11, there were no open files, and no error message. Go figure!