Additional validation so we don't get caught off guard with a nil response

if CommonAPI ever prevents us from injecting this data

test/pleroma/web/activity_pub/transmogrifier_test.exs

@@ -208,6 +208,12 @@ test "it strips internal fields" do
           application: %{name: "TestClient", website: "https://pleroma.social"}
         })
 
+      # Ensure injected application data made it into the activity
+      # as we don't have a Token to derive it from, otherwise it will
+      # be nil and the test will pass
+      assert %{"application" => %{name: "TestClient", website: "https://pleroma.social"}} =
+               activity.object.data
+
       {:ok, modified} = Transmogrifier.prepare_outgoing(activity.data)
 
       assert length(modified["object"]["tag"]) == 2