file upload error into book created from opf

[Elvis003]

Error while uploading any file into existing book created from opf file on Windows 10 using Calibre Portable
opf file attached

calibre, version 5.8.1
CHYBA: Neošetřená výjimka: <b>TypeError</b>:cannot unpack non-iterable bool object

calibre 5.8.1 Portable embedded-python: True is64bit: False
Windows-10-10.0.19041 Windows ('32bit', 'WindowsPE')
32bit process running on 64bit windows
('Windows', '10', '10.0.19041')
Python 3.8.5
Windows: ('10', '10.0.19041', '', 'Multiprocessor Free')
Interface language: cs
Successfully initialized third party plugins: DOC Input (1, 0, 1) && Extract ISBN (1, 5, 0) && Kindle Collections (1, 7, 26)
Traceback (most recent call last):
  File "calibre\gui2\actions\add.py", line 455, in files_dropped_on_book
TypeError: cannot unpack non-iterable bool object