Fix: Exclude unset fields in OpenAIConversationsSession.get_items() (#1883)

Author: ihower

src/agents/memory/openai_conversations_session.py

@@ -50,15 +50,15 @@ async def get_items(self, limit: int | None = None) -> list[TResponseInputItem]:
                 order="asc",
             ):
                 # calling model_dump() to make this serializable
-                all_items.append(item.model_dump())
+                all_items.append(item.model_dump(exclude_unset=True))
         else:
             async for item in self._openai_client.conversations.items.list(
                 conversation_id=session_id,
                 limit=limit,
                 order="desc",
             ):
                 # calling model_dump() to make this serializable
-                all_items.append(item.model_dump())
+                all_items.append(item.model_dump(exclude_unset=True))
                 if limit is not None and len(all_items) >= limit:
                     break
             all_items.reverse()