"find_or_default" error when reloading with some plugins which use "deface" gem in Redmine 5.1 environment

[sanak]

I encountered the following error when reloading with some plugins which use deface gem in Redmine 5.1-stable branch environment.

RuntimeError (There's no setting named plugin_redmine_message_customize):
  
app/models/setting.rb:361:in `find_or_default'
plugins/redmine_message_customize/app/models/custom_message_setting.rb:6:in `find_or_default'
plugins/redmine_message_customize/config/locales/custom_messages/ar.rb:1:in `load_rb'
plugins/redmine_custom_fields_groups/app/overrides/issues.rb:2:in `new'
plugins/redmine_custom_fields_groups/app/overrides/issues.rb:2:in `<module:Issues>'
plugins/redmine_custom_fields_groups/app/overrides/issues.rb:1:in `<top (required)>'
plugins/redmine_custom_fields_groups/init.rb:29:in `require_relative'
plugins/redmine_custom_fields_groups/init.rb:29:in `<top (required)>'
lib/redmine/plugin_loader.rb:31:in `load'
lib/redmine/plugin_loader.rb:31:in `run_initializer'
lib/redmine/plugin_loader.rb:108:in `each'
lib/redmine/plugin_loader.rb:108:in `block in load'

But, I couldn't find which plugin side causes the error, because deface side seems to require some hacks.
(But, sorry. I haven't checked the details about deface side yet... 🙇💦)
https://github.com/jbbarth/redmine_base_deface/blob/master/init.rb#L13-L39

If someone know what could be the cause, telling us is really helpful... 🙏 🙇‍♂️

Here is my minimum reproducible steps in one of our plugins which use deface gem.

1. Setup env

   git clone git@github.com:redmine/redmine.git -b 5.1-stable redmine-message-customize
   cd redmine-message-customize
   # Create and adjust config/database.yml (We are using "postgresql" adapter)
   cd plugins
   git clone git@github.com:farend/redmine_message_customize.git
   git clone git@github.com:gtt-project/redmine_custom_fields_groups.git
   cd ../
   bundle install
   bundle exec rake db:create
   bundle exec rake db:migrate
   bundle exec rake db:fixtures:load
   bundle exec rake redmine:plugins:migrate

2. Launch rails server

   bundle exec rails s -b 0

3. Open http://localhost:3000 with a browser, then login and move to /projects path.
4. Modify message customize plugin's ja locale file.

   --- a/config/locales/ja.yml
   +++ b/config/locales/ja.yml
   :
   -  label_default_messages: デフォルトのメッセージを確認する
   +  label_default_messages: デフォルトのメッセージを確認する123

5. Reload the browser, then you will see the description top error message.

[sanak]

From some investigate, the error cause seems to be our plugin side's insufficient Zeitwerk support.
Because the following custom_fields_groups plugin's side change, the above error doesn't happen.
gtt-project/redmine_custom_fields_groups#38

I close this issue and sorry for bothering. 🙇‍♂️💦