Fix logs command without argument in thread channel when the recipient is not cached.

Author: Jerrie-Aries

cogs/modmail.py

@@ -680,7 +680,7 @@ async def logs(self, ctx, *, user: User = None):
             thread = ctx.thread
             if not thread:
                 raise commands.MissingRequiredArgument(SimpleNamespace(name="member"))
-            user = thread.recipient
+            user = thread.recipient or await self.bot.fetch_user(thread.id)
 
         default_avatar = "https://cdn.discordapp.com/embed/avatars/0.png"
         icon_url = getattr(user, "avatar_url", default_avatar)