Error while exiting the application (BS 11)

After installing a new 11th version of BS, I encounter the following issue while quitting the program.
1. If the current folder is References:

BS always generates the error shown above.

2. If the current folder is not References (e.g. Categories):

BS never generates the error.

OS: Windows 10 x64

Besides, it is desirable to add the item "11.x" in the list "Versions:" on the forum topic form.