fix(userbot): encode absent pyrogram raw payloads as empty json

backend/src/userbot/modules/raw_json.py

@@ -0,0 +1,8 @@
+from pyrogram.raw.core import TLObject
+from pyrogram.types import Object
+
+EMPTY_JSON = "{}"
+
+
+def raw_json(obj: Object | TLObject | None) -> str:
+    return EMPTY_JSON if obj is None else str(obj)