Merge pull request woocommerce#9290 from woothemes/issue/9166-reset-o…

…rder-customer-id-on-user-delete

When a WordPress user is deleted, turn any orders they have into Guest orders.

includes/wc-user-functions.php

@@ -537,3 +537,14 @@ function wc_get_customer_order_count( $user_id ) {
 
 	return absint( $count );
 }
+
+/**
+ * Reset _customer_user on orders when a user is deleted.
+ * @param int $user_id
+ */
+function wc_reset_order_customer_id_on_deleted_user( $user_id ) {
+	global $wpdb;
+
+	$wpdb->update( $wpdb->postmeta, array( '_customer_user' => 0 ), array( '_customer_user' => $user_id ) );
+}
+add_action( 'deleted_user', 'wc_reset_customer_id_on_delete_user' );