[jbacelar]

After having carried out an import of authors-nationality without any problem, in the second import with new authors this error appears:

calibre, version 5.31.1
ERROR: Excepción no considerada: <b>AttributeError</b>:'set' object has no attribute 'append'

calibre 5.31.1 [64bit] embedded-python: True is64bit: True
Windows-10-10.0.19041 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.19041')
Python 3.8.5
Windows: ('10', '10.0.19041', '', 'Multiprocessor Free')
Interface language: es
Successfully initialized third party plugins: DeDRM (7, 2, 1) && Action Chains (1, 13, 3) && Calibre Power Search Plugin (2, 1, 1) && Category Tags (0, 1, 1) && Comments Cleaner (1, 4, 1) && Count Pages (1, 11, 1) && Diaps Editing Toolbag (0, 3, 7) && EpubCheck (0, 2, 3) && EpubMerge (2, 11, 0) && EpubSplit (3, 1, 0) && Favourites Menu (1, 0, 5) && Find Duplicates (1, 8, 10) && GetFileName (0, 1, 1) && Import List (1, 5, 6) && Job Spy (1, 0, 190) && LanguageTool (0, 1, 1) && Modify ePub (1, 6, 3) && Prince PDF (1, 5, 0) && Quality Check (1, 11, 4) && Resize Cover (1, 1, 0) && Search The Internet (1, 8, 1) && TOC View Generator (2, 1, 1) && User Category (1, 5, 5) && View Manager (1, 6, 0)
Traceback (most recent call last):
File "calibre_plugins.category_tags.user_categories.pag e_resolve", line 699, in validatePage
File "calibre_plugins.category_tags.user_categories.act ions", line 115, in add_categories_for_item
AttributeError: 'set' object has no attribute 'append'