KeyError when trying to run `swh graph rpc-serve`

$ swh graph rpc-serve -g swh/graph/tests/dataset/compressed/example.graph 
[…]
 Traceback (most recent call last):
  File "VENV/bin/swh", line 8, in <module>
    sys.exit(main())
[…]
  File "VENV/lib/python3.10/site-packages/click/decorators.py", line 26, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "HOME/swh-environment/swh-graph/swh/graph/cli.py", line 135, in serve
    config["graph"]["grpc_server"]["path"] = graph
KeyError: 'grpc_server'