erp5_json_rpc_api: bypass strange jsonform behaviour

master/bt5/erp5_json_rpc_api/DocumentTemplateItem/portal_components/document.erp5.JsonRpcAPIService.py

@@ -352,7 +352,8 @@ class JsonRpcAPIService(OpenAPIService):
     except jsonschema.exceptions.ValidationError as e:
       raise JsonRpcAPIInvalidJsonDictContent(str(e))
     response = request.RESPONSE
-    if response.getHeader('Content-Type'):
-      return result
+    # XXX Hardcoded JSONForm behaviour
+    if result == "Nothing to do":
+      result = {}
     response.setHeader("Content-Type", "application/json")
     return json.dumps(result).encode()