Use correct activity for undo

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -142,7 +142,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
 
   def unannounce(%User{} = actor, %Object{} = object, local \\ true) do
     with %Activity{} = activity <- get_existing_announce(actor.ap_id, object),
-         unannounce_data <- make_unannounce_data(actor, object),
+         unannounce_data <- make_unannounce_data(actor, activity),
          {:ok, unannounce_activity} <- insert(unannounce_data, local),
          :ok <- maybe_federate(activity),
          {:ok, _activity} <- Repo.delete(activity),

lib/pleroma/web/activity_pub/utils.ex

@@ -283,13 +283,13 @@ defmodule Pleroma.Web.ActivityPub.Utils do
   """
   def make_unannounce_data(
         %User{ap_id: ap_id} = user,
-        %Object{data: %{"id" => id, "context" => context}} = object
+        %Activity{data: %{"id" => id, "context" => context}} = activity
       ) do
     %{
       "type" => "Undo",
       "actor" => ap_id,
       "object" => id,
-      "to" => [user.follower_address, object.data["actor"]],
+      "to" => [user.follower_address, activity.data["actor"]],
       "cc" => ["https://www.w3.org/ns/activitystreams#Public"],
       "context" => context
     }