When registering language codes, there is a small typo that forces the WordPress default locale to be added to the language code enums even if Polylang codes were already added.
Thanks! Uh,empty() seems really dangerous tool since it hides the undefined variable -notices which would have been caught by the tests. Better use count() next time...
When registering language codes, there is a small typo that forces the WordPress default locale to be added to the language code enums even if Polylang codes were already added.