WP_SCRIPTS :: Localize disebut salah.
# Befor
wp_localize_script( 'wlsm-admin', 'wlsmloadingtext', 'Loading...');
# After
wp_localize_script( 'wlsm-admin', 'wlsmloadingtext', ['Loading...'] );
you can fix that by passing in an array
Darkvent