Erreur Internal Server Error à partir de la V4.1.0 et suivante

[quick-tutoriel]

J'utilise Glances dans un container et depuis la version 4.1.0, j'ai systématiquement l'erreur "Internal Server Error"
Je précise que j'utilise Glances avec l'images Docker.
Voici les logs :
` raise exc

File "/venv/lib/python3.11/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app

await app(scope, receive, sender)

File "/venv/lib/python3.11/site-packages/starlette/routing.py", line 72, in app

response = await func(request)

           ^^^^^^^^^^^^^^^^^^^

File "/venv/lib/python3.11/site-packages/fastapi/routing.py", line 278, in app

raw_response = await run_endpoint_function(

               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

File "/venv/lib/python3.11/site-packages/fastapi/routing.py", line 193, in run_endpoint_function

return await run_in_threadpool(dependant.call, **values)

       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

File "/venv/lib/python3.11/site-packages/starlette/concurrency.py", line 42, in run_in_threadpool

return await anyio.to_thread.run_sync(func, *args)

       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

File "/venv/lib/python3.11/site-packages/anyio/to_thread.py", line 56, in run_sync

return await get_async_backend().run_sync_in_worker_thread(

       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

File "/venv/lib/python3.11/site-packages/anyio/_backends/_asyncio.py", line 2177, in run_sync_in_worker_thread

return await future

       ^^^^^^^^^^^^

File "/venv/lib/python3.11/site-packages/anyio/_backends/_asyncio.py", line 859, in run

result = context.run(func, *args)

         ^^^^^^^^^^^^^^^^^^^^^^^^

File "/app/glances/outputs/glances_restful_api.py", line 342, in _index

self.__update__()

File "/app/glances/outputs/glances_restful_api.py", line 160, in update

self.stats.update()

File "/app/glances/stats.py", line 269, in update

self.__update_plugin(p)

File "/app/glances/stats.py", line 258, in __update_plugin

self._plugins[p].update()

File "/app/glances/plugins/plugin/model.py", line 1151, in wrapper

ret = fct(self, *args, **kw)

      ^^^^^^^^^^^^^^^^^^^^^^

File "/app/glances/plugins/plugin/model.py", line 1168, in wrapper

ret = fct(*args, **kw)

      ^^^^^^^^^^^^^^^^

File "/app/glances/plugins/cpu/init.py", line 165, in update

stats = self.update_local()

        ^^^^^^^^^^^^^^^^^^^

File "/app/glances/plugins/plugin/model.py", line 1226, in wrapper

compute_rate(self, stats, self.stats_previous)

File "/app/glances/plugins/plugin/model.py", line 1195, in compute_rate

stat[field] = stat[field] - stat_previous[field + '_gauge']

              ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

TypeError: unsupported operand type(s) for -: 'NoneType' and 'NoneType'`

Si j'utilise une version de l'image Docker <4.1.0, tout fonctionne correctement.

[nicolargo]

Add a test to avoid this error.

Pushed on the develop branch.

Thanks for the issue report @quick-tutoriel !