I'm currently experiencing the same error (edit: as @Milotic) on two separate devices. I have not installed any other modifications for the game. Debug logs below as code snippets (due to file type limitations).
# guiDebug.log
ERROR:root:json_loadError:
Traceback (most recent call last):
File "gui.py", line 321, in __init__
File "json\__init__.py", line 299, in load
File "json\__init__.py", line 354, in loads
File "json\decoder.py", line 339, in decode
File "json\decoder.py", line 357, in raw_decode
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
# gecDebug.log - empty