Fixes error when receiving Undo for unknown boost

bookwyrm/activitypub/verbs.py

@@ -70,6 +70,9 @@ class Undo(Verb):
         if self.object.type == "Follow":
             model = apps.get_model("bookwyrm.UserFollows")
         obj = self.object.to_model(model=model, save=False, allow_create=False)
+        if not obj:
+            # if we don't have the object, we can't undo it. happens a lot with boosts
+            return
         obj.delete()
 
 

bookwyrm/tests/views/test_inbox.py

@@ -563,6 +563,23 @@ class Inbox(TestCase):
         }
         views.inbox.activity_task(activity)
 
+    def test_handle_unboost_unknown_boost(self):
+        """ undo a boost """
+        activity = {
+            "type": "Undo",
+            "actor": "hi",
+            "id": "bleh",
+            "to": ["https://www.w3.org/ns/activitystreams#public"],
+            "cc": ["https://example.com/user/mouse/followers"],
+            "object": {
+                "type": "Announce",
+                "id": "http://fake.com/unknown/boost",
+                "actor": self.remote_user.remote_id,
+                "object": self.status.remote_id,
+            },
+        }
+        views.inbox.activity_task(activity)
+
     def test_handle_add_book_to_shelf(self):
         """ shelving a book """
         work = models.Work.objects.create(title="work title")