The library language files are being loaded after the system plugins are imported and the onAfterInitialise event is dispatched. Move this loading to before the plugins are loaded and dispatched.
Testing Instructions
Language files are still loaded correctly.
Documentation Changes Required
If anyone has a custom CMS application subclass with a loadLibraryLanguage() method and the signature doesn't match what's added here, they'll get notices.
I have tested this item✅ successfully on 1da978f
This comment was created with the J!Tracker Application at issues.joomla.org/joomla-cms/11842.