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

backend/src/userbot/handlers/raw/read_contents.py

@@ -4,6 +4,7 @@ from pyrogram import raw, utils
 
 from userbot import PyroClient
 from userbot.modules.capture.chat_meta import meta_from_chat_id
+from userbot.modules.raw_json import raw_json
 from userbot.modules.read_receipts import repository as receipts
 from userbot.modules.stt import repository
 from userbot.modules.stt.gate import safe_transcribe
@@ -41,7 +42,7 @@ async def handle(
                 cand_chat_id,
                 datetime.now(UTC),
                 message_id,
-                str(update),
+                raw_json(update),
             )
             continue
         if not untranscribed: