Fix authenticate_none method, via #438

authlib/oauth2/rfc6749/authenticate_client.py

@@ -85,7 +85,7 @@ def authenticate_none(query_client, request):
     does not have a client secret.
     """
     client_id = request.client_id
-    if client_id and 'client_secret' not in request.data:
+    if client_id and not request.data.get('client_secret'):
         client = _validate_client(query_client, client_id, request.state)
         log.debug(f'Authenticate {client_id} via "none" success')
         return client