FIxed issue with AP actors without attachments

retribute_api/search/activitypub.py

@@ -55,5 +55,7 @@ class ActorSerializer(serializers.Serializer):
     id = serializers.URLField()
     summary = serializers.CharField(required=False)
     url = serializers.URLField(required=False)
-    attachment = serializers.ListField(child=AttachmentSerializer(), min_length=1)
+    attachment = serializers.ListField(
+        child=AttachmentSerializer(), min_length=0, required=False
+    )
     tag = serializers.ListField(child=TagSerializer(), min_length=0)