Fatal error with custom_override_checkout_fields

Hello there,

I added the following snippet in the plugin “code snippet”:

add_filter( 'woocommerce_default_address_fields' , 'custom_override_default_address_fields' );

function custom_override_checkout_fields( $fields ) {
     $address_fields['order']['billing_state']['placeholder'] = 'BTW-nummer';
     $address_fields['order']['billing_state']['label'] = 'BTW-nummer';
     return $address_fields;
}

It worked for a few months, but now it is causing a fatal error when trying to access the cart page. I now have disabled it but I need this function.

Any idea on what I can try to solve this?

Thanks in advance !

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