SideEffects: Don't delete a deleted object twice.

lib/pleroma/web/activity_pub/side_effects.ex

@@ -253,6 +253,9 @@ def handle(%{data: %{"type" => "Delete", "object" => deleted_object}} = object,
 
     result =
       case deleted_object do
+        %Object{data: %{"type" => "Tombstone"}} ->
+          :ok
+
         %Object{} ->
           with {:ok, deleted_object, activity} <- Object.delete(deleted_object),
                {_, actor} when is_binary(actor) <- {:actor, deleted_object.data["actor"]},

test/web/activity_pub/side_effects_test.exs

@@ -238,6 +238,15 @@ test "it logs issues with objects deletion", %{
                {:error, :no_object_actor} = SideEffects.handle(delete)
              end) =~ "object doesn't have an actor"
     end
+
+    test "it works with double deletions", %{
+      delete: delete,
+      object: object
+    } do
+      assert {:ok, activity, _} = SideEffects.handle(delete)
+      Object.invalid_object_cache(object)
+      assert {:ok, ^activity, _} = SideEffects.handle(delete)
+    end
   end
 
   describe "EmojiReact objects" do