How to fix this woocommerce issue?

Question

WordPress

Please help fix this problem.
Warning: Invalid argument supplied for foreach() in /www/wp-content/plugins/woocommerce/includes/class-wc-checkout.php on line 267
Here's what's in the function itself:
foreach ( $this->fields as $field_type = > $fields ) {
// Sort each of the checkout field sections based on priority.
uasort( $this->fields[ $field_type ], 'wc_checkout_fields_uasort_comparison' );