Error when filtering with 'python -m pandoc_fignos json'

[siprbaum]

EDITED: to fix copy&paste error for the table.md content

I have a quite strange behaviour that when using the pandoc-fignos filter via python, e.g. using
cat document.json| python -m pandoc_fignos json # this one fails
instead of
cat document.json| pandoc -F pandoc-fignos json # this one succeeds

So the filtering with the direct call to python was done to have a tight control on the python installation, e.g.
we use a pre-packaged self contained python version including pandoc-fignos.
This used to work with a very old pandoc version 2.2.1, but I noticed when trying to upgrade to the latest and greatest
pandoc version 2.14.0.3 the direct filtering with python -m pandoc fails.

Reproducer:

table.md content:

Version | Status | Date of Issue
-|:-:|:-:
01| draft | 2021-06-03

Reproducer script

echo "#### PANDOC VERSION ####"
pandoc --version
echo ""

echo "#### pandoc-fignos VERSION ####"
pandoc-fignos --version

echo "#### running reproducer ####"
pandoc --from markdown+pipe_tables --to json table.md | pandoc --from json --to json --output table.json

# This works
echo "#### Filtering with 'pandoc -F pandoc-fignos' ####"
cat table.json | pandoc -F pandoc-fignos --from json --to gfm

echo ""

# This doesn't work
echo "#### Filtering with 'python -m pandoc_fignos json' ####"
cat table.json | python -m pandoc_fignos json | pandoc --from json --to gfm

Output:

#### PANDOC VERSION ####                                                                                                                 
pandoc.exe 2.14.0.3                                                                                                                      
Compiled with pandoc-types 1.22, texmath 0.12.3, skylighting 0.10.5.2,                                                                   
citeproc 0.4.0.1, ipynb 0.1.0.1                                                                                                          
User data directory: C:\Users\z002bd7y\AppData\Roaming\pandoc                                                                            
Copyright (C) 2006-2021 John MacFarlane. Web:  https://pandoc.org                                                                        
This is free software; see the source for copying conditions. There is no                                                                
warranty, not even for merchantability or fitness for a particular purpose.                                                              
                                                                                                                                         
#### pandoc-fignos VERSION ####                                                                                                          
pandoc-fignos 2.4.0                                                                                                                      
#### running reproducer ####                                                                                                             
#### Filtering with 'pandoc -F pandoc-fignos' ####                                                                                       
| Version | Status | Date of Issue |
|---------|:------:|:-------------:|
| 01      | draft  |  2021-06-03   |
                                                                                                                                         
#### Filtering with 'python -m pandoc_fignos json' ####                                                                                  
Traceback (most recent call last):                                                                                                       
  File "C:\src\gitlab\document\docgen\python\lib\runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "C:\src\gitlab\document\docgen\python\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "C:\src\gitlab\document\docgen\python\lib\site-packages\pandoc_fignos.py", line 669, in <module>
    main()
  File "C:\src\gitlab\document\docgen\python\lib\site-packages\pandoc_fignos.py", line 651, in main                                      
    altered)
  File "C:\src\gitlab\document\docgen\python\lib\site-packages\pandoc_fignos.py", line 648, in <lambda>
    altered = functools.reduce(lambda x, action: walk(x, action, fmt, meta),
  File "C:\src\gitlab\document\docgen\python\lib\site-packages\pandocfilters.py", line 111, in walk
    item['c'] if 'c' in item else None, format, meta)
  File "C:\src\gitlab\document\docgen\python\lib\site-packages\pandocxnos\core.py", line 871, in process_refs
    _process_refs(value[-5], pattern, labels)
  File "C:\src\gitlab\document\docgen\python\lib\site-packages\pandocxnos\core.py", line 95, in wrapper
    ret = func(*args, **kwargs)
  File "C:\src\gitlab\document\docgen\python\lib\site-packages\pandocxnos\core.py", line 770, in _process_refs
    if v['t'] == 'Cite' and len(v['c']) == 2:
TypeError: 'NoneType' object is not subscriptable                                                                                        
JSON parse error: Error in $: not enough input