Fix admin outbox query

app/boxes.py

@@ -454,6 +454,7 @@ async def get_outbox_object_by_ap_id(
     db_session: AsyncSession, ap_id: str
 ) -> models.OutboxObject | None:
     return (
+        (
             await db_session.execute(
                 select(models.OutboxObject)
                 .where(models.OutboxObject.ap_id == ap_id)
@@ -465,13 +466,16 @@ async def get_outbox_object_by_ap_id(
                         joinedload(models.InboxObject.actor),
                     ),
                     joinedload(models.OutboxObject.relates_to_outbox_object).options(
-                    joinedload(models.OutboxObject.outbox_object_attachments).options(
-                        joinedload(models.OutboxObjectAttachment.upload)
-                    ),
+                        joinedload(
+                            models.OutboxObject.outbox_object_attachments
+                        ).options(joinedload(models.OutboxObjectAttachment.upload)),
                     ),
                 )
             )
-    ).scalar_one_or_none()  # type: ignore
+        )
+        .unique()
+        .scalar_one_or_none()
+    )  # type: ignore
 
 
 async def get_anybox_object_by_ap_id(