Don't worry about setting creator for invite

synapse/storage/databases/main/room.py

@@ -1440,6 +1440,11 @@ async def upsert_room_on_join(
 
         room_creator = create_event.content.get("creator", None)
 
+        if room_creator is None:
+            # If the create event does not have a creator then the room is
+            # invalid, and it would fail auth checks anyway.
+            raise StoreError(400, "No creator defined on the create event")
+
         await self.db_pool.simple_upsert(
             desc="upsert_room_on_join",
             table="rooms",
@@ -1467,9 +1472,6 @@ async def maybe_store_room_on_outlier_membership(
         # mark the room as having an auth chain cover index.
         has_auth_chain_index = await self.has_auth_chain_index(room_id)
 
-        create_event = await self.get_create_event_for_room(room_id)
-        room_creator = create_event.content.get("creator", None)
-
         await self.db_pool.simple_upsert(
             desc="maybe_store_room_on_outlier_membership",
             table="rooms",
@@ -1478,7 +1480,10 @@ async def maybe_store_room_on_outlier_membership(
             insertion_values={
                 "room_version": room_version.identifier,
                 "is_public": False,
-                "creator": room_creator,
+                # We don't worry about setting the `creator` here because
+                # we don't process any messages in a room while a user is
+                # invited (only after the join).
+                "creator": "",
                 "has_auth_chain_index": has_auth_chain_index,
             },
             # rooms has a unique constraint on room_id, so no need to lock when doing an