Finished fixing add_download_task_from_url. Without any errors this t…

…ime !

src/freebox_api/access.py

@@ -143,6 +143,7 @@ async def post(
         """
         Send post request and return results
         """
+        data: Optional[str|Any] = None
         if json_transform:
             data = json.dumps(payload) if payload else None
         else: