fix(notifications): skip the filter check for objects without content

Regex.match? raised on objects without content (for example posts with
only attachments), so no notifications were created for them when the
recipient had an irreversible filter.

test/pleroma/notification_test.exs

@@ -9,6 +9,7 @@ defmodule Pleroma.NotificationTest do
 
   alias Pleroma.FollowingRelationship
   alias Pleroma.Notification
+  alias Pleroma.Object
   alias Pleroma.Repo
   alias Pleroma.Tests.ObanHelpers
   alias Pleroma.User
@@ -276,6 +277,22 @@ defmodule Pleroma.NotificationTest do
       assert {:ok, []} == Notification.create_notifications(status)
     end
 
+    test "it creates notifications for objects without content when the user has filters" do
+      author = insert(:user)
+      user = insert(:user)
+      insert(:filter, user: user, phrase: "cofe", hide: true)
+
+      {:ok, status} = CommonAPI.post(author, %{status: "hey @#{user.nickname}"})
+      object = Object.normalize(status, fetch: false)
+
+      {:ok, _} =
+        object
+        |> Object.change(%{data: Map.delete(object.data, "content")})
+        |> Object.update_and_set_cache()
+
+      assert {:ok, [_]} = Notification.create_notifications(Pleroma.Activity.get_by_id(status.id))
+    end
+
     test "it creates notifications if content matches with a not irreversible filter" do
       user = insert(:user)
       subscriber = insert(:user)