Don't error when we don't have a parent post

activities/services/post.py

@@ -97,7 +97,7 @@ class PostService:
         ancestors: list[Post] = []
         ancestor = self.post
         while ancestor.in_reply_to and len(ancestors) < num_ancestors:
-            ancestor = self.queryset().get(object_uri=ancestor.in_reply_to)
+            ancestor = self.queryset().filter(object_uri=ancestor.in_reply_to).first()
             if ancestor is None:
                 break
             if ancestor.state in [PostStates.deleted, PostStates.deleted_fanned_out]: