Transmogrifier: Do not crash if inReplyTo does not exist and can't be fetched

lib/pleroma/web/activity_pub/transmogrifier.ex

@@ -339,7 +339,7 @@ def fix_content_map(object), do: object
   def fix_type(%{"inReplyTo" => reply_id} = object) when is_binary(reply_id) do
     reply = Object.normalize(reply_id)
 
-    if reply.data["type"] == "Question" and object["name"] do
+    if reply && (reply.data["type"] == "Question" and object["name"]) do
       Map.put(object, "type", "Answer")
     else
       object

test/web/activity_pub/transmogrifier_test.exs

@@ -60,6 +60,22 @@ test "it fetches replied-to activities if we don't have them" do
       assert returned_object.data["inReplyToAtomUri"] == "https://shitposter.club/notice/2827873"
     end
 
+    test "it does not crash if the object in inReplyTo can't be fetched" do
+      data =
+        File.read!("test/fixtures/mastodon-post-activity.json")
+        |> Poison.decode!()
+
+      object =
+        data["object"]
+        |> Map.put("inReplyTo", "https://nonexistent.space/whatever")
+
+      data =
+        data
+        |> Map.put("object", object)
+
+      {:ok, _returned_activity} = Transmogrifier.handle_incoming(data)
+    end
+
     test "it works for incoming notices" do
       data = File.read!("test/fixtures/mastodon-post-activity.json") |> Poison.decode!()