Ok my WP is up to date. And Polylang do the same thing. The var $pll_current_language() return a bool false, all my settings in CP of Polylang are lost, and i can't add a new language because i have "Fatal error: Cannot use object of type WP_Error as array in /public_html/wptest/wp-content/plugins/polylang/admin/admin-model.php on line 47"
I think i'll just become mad :x