[DNSB]

Originally Posted by kovidgoyal

@DNSB what error do you get?

If I don't have an MTP device connected and attempt to open the MTP device configuration page from Preferences/Plugins, instead of the Cannot configure I get from 4.23, 5.4.2 gives the following error message:

Spoiler:

calibre, version 5.4.2
ERROR: Unhandled exception: <b>TypeError</b>:'<' not supported between instances of 'NoneType' and 'str'

calibre 5.4.2 [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: None
Successfully initialized third party plugins: DeDRM (7, 0, 0) && Annotations (1, 13, 0) && Baen (1, 2, 0) && Barnes & Noble (1, 2, 16) && Calibre Power Search Plugin (1, 7, 0) && Count Pages (1, 11, 0) && Diaps Editing Toolbag (0, 3, 7) && EpubCheck (0, 2, 3) && EpubMerge (2, 11, 0) && EpubSplit (3, 0, 0) && FanFicFare (3, 24, 0) && Fantastic Fiction (1, 4, 0) && Find Duplicates (1, 8, 3) && Goodreads (1, 5, 1) && Hyphenate This! (0, 1, 3) && Job Spy (1, 0, 188) && Kindle hi-res covers (0, 5, 0) && KindleUnpack - The Plugin (0, 82, 3) && Kobo Books (1, 8, 0) && Kobo Utilities (2, 11, 9) && KoboTouchExtended (3, 4, 1) && Modify ePub (1, 6, 1) && Obok DeDRM (6, 7, 0) && Open With (1, 5, 13) && Quality Check (1, 10, 1) && Resize Cover (1, 1, 0) && ScrambleEbook (0, 4, 5) && SmartEject (2, 3, 0) && Smashwords Metadata (1, 0, 2)
Traceback (most recent call last):
  File "calibre\gui2\preferences\plugins.py", line 293, in customize_plugin
  File "calibre\gui2\preferences\plugins.py", line 371, in modify_plugin
  File "calibre\customize\__init__.py", line 158, in do_user_config
  File "calibre\devices\mtp\driver.py", line 532, in config_widget
  File "calibre\gui2\device_drivers\mtp_config.py", line 408, in __init__
  File "calibre\gui2\device_drivers\mtp_config.py", line 450, in get_pref
  File "calibre\utils\config.py", line 437, in __setitem__
  File "calibre\utils\config.py", line 400, in commit
  File "calibre\utils\config.py", line 421, in to_raw
  File "calibre\utils\config_base.py", line 101, in json_dumps
  File "json\__init__.py", line 234, in dumps
  File "json\encoder.py", line 201, in encode
  File "json\encoder.py", line 431, in _iterencode
  File "json\encoder.py", line 353, in _iterencode_dict
TypeError: '<' not supported between instances of 'NoneType' and 'str'

If I plug in my Nexus 7 and tell it to transfer files, the configuration dialog opens without problems.