"nontype" object is not subsertable

[liu-hz]

error decoding response body: invalid type: null, expected a string at line 1 column 80⁩ on the ankidesktop 2.1.41.

i use the python 3.9 it not work show the same error
how i can fix this problem , who can help me

[liu-hz]

File "/usr/lib/python3.9/wsgiref/handlers.py", line 137, in run
self.result = application(self.environ, self.start_response)
File "/usr/local/lib/python3.9/dist-packages/webob/dec.py", line 129, in call
resp = self.call_func(req, *args, **kw)
File "/usr/local/lib/python3.9/dist-packages/webob/dec.py", line 193, in call_func
return self.func(req, *args, **kwargs)
File "/anki-sync-server/src/ankisyncd/sync_app.py", line 523, in call
result = self._execute_handler_method_in_thread(url, data, session)
File "/anki-sync-server/src/ankisyncd/sync_app.py", line 588, in _execute_handler_method_in_thread
result = thread.execute(run_func, kw=keyword_args)
File "/anki-sync-server/src/ankisyncd/thread.py", line 79, in execute
raise ret
File "/anki-sync-server/src/ankisyncd/thread.py", line 98, in _run
ret = self.wrapper.execute(func, args, kw, return_queue)
File "/anki-sync-server/src/ankisyncd/collection.py", line 45, in execute
ret = func(*args, **kw)
File "/anki-sync-server/src/ankisyncd/sync_app.py", line 579, in run_func
res = handler_method(**keyword_args)
File "/anki-sync-server/src/ankisyncd/sync_app.py", line 124, in start
self.remove(graves)
File "/anki-sync-server/src/ankisyncd/sync.py", line 303, in remove
self.col.remove_cards_and_orphaned_notes(graves['cards'])
TypeError: 'NoneType' object is not subscriptable

use the python 3.9 it not work