Merge Books Functionality Broken in version 7.13

[Dave]

When attempting to merge two epubs, I get 'TypeError: cannot unpack non0iterable bool object'. The details are as follows:
calibre, version 7.13.0
ERROR: Unhandled exception: <b>TypeError</b>:cannot unpack non-iterable bool object

calibre 7.13 embedded-python: True
Windows-10-10.0.22631-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.22631')
Python 3.11.5
Windows: ('10', '10.0.22631', 'SP0', 'Multiprocessor Free')
Interface language: None
EXE path: C:\Program Files\Calibre2\calibre.exe
Successfully initialized third party plugins: Gather KFX-ZIP (from KFX Input) (2, 15, 0) && DeDRM (10, 0, 3) && Package KFX (from KFX Input) (2, 15, 0) && Amazon.com Multiple Countries (1, 0, 0) && Annotations (1, 17, 13) && Audit Log (1, 0, 19) && Author Book Count (2, 2, 3) && Baen (1, 1, 0) && Barnes & Noble (1, 5, 5) && Category Tags (0, 2, 8) && Clean Comments (0, 2, 1) && Clean Metadata (0, 0, 6) && Count Pages (1, 13, 6) && Embed Comic Metadata (1, 6, 6) && Extract ISBN (1, 6, 3) && Fantastic Fiction (1, 7, 0) && Fantastic Fiction Adults (1, 3, 1) && FictionDB (1, 4, 2) && Find Duplicates (1, 10, 9) && Generate Cover (2, 3, 4) && Goodreads (1, 8, 2) && Goodreads Sync (1, 16, 8) && KFX metadata reader (from KFX Input) (2, 15, 0) && From KFX (2, 15, 0) && KFX Input (2, 15, 0) && Kindle hi-res covers (0, 5, 1) && Kobo Books (1, 9, 2) && Kobo Metadata (1, 6, 2) && Library Codes (1, 0, 65) && Manage Series (1, 5, 2) && Modify ePub (1, 8, 3) && OverDrive Libby (0, 1, 9) && Overdrive Link (2, 57, 0) && PDF Cover (0, 1, 0) && Quality Check (1, 13, 10) && Resize Cover (1, 2, 1) && Save To Format (0, 0, 6) && Search The Internet (1, 11, 2) && Smashwords Metadata (1, 0, 2) && Standard Ebooks (1, 0, 0) && TTS to MP3 (0, 6, 0) && TextDiff (1, 2, 4) && User Category (1, 6, 1) && View Manager (1, 10, 3) && ePub Extended Metadata {Writer} (0, 11, 2) && ePub Extended Metadata {Reader} (0, 11, 2) && ePub Extended Metadata (0, 11, 2) && Overdrive Link Metadata Source (2, 57, 0)
Traceback (most recent call last):
  File "calibre\gui2\actions\edit_metadata.py", line 644, in merge_books
TypeError: cannot unpack non-iterable bool object