Bug Report

• Yes, I reviewed the contribution guidelines.
• Yes, more specifically, I reviewed the guidelines on how to write clear bug reports.

Describe the current, buggy behavior

Running wp role reset <role> for missing role (or using --all) results in fatal error in PHP 8.

Describe how other contributors can replicate this bug

• run wp role delete editor
• run wp role reset editor
• see Error: There has been a critical error on this website.Learn more about troubleshooting WordPress.type1messageUncaught TypeError: array_diff_key(): Argument #2 must be of type array, null given in phar:///usr/local/bin/wp/vendor/wp-cli/role-command/src/Role_Command.php:362

This only affects the reporting of the reset, the role is successfully restored ahead of the error.

Describe what you would expect as the correct outcome

No error. Success message/notice.

Let us know what environment you are running this on

$ wp --info
OS:	Linux 5.10.0-16-amd64 #1 SMP Debian 5.10.127-2 (2022-07-23) x86_64
Shell:	/bin/bash
PHP binary:	/usr/local/php8.1/bin/php
PHP version:	8.1.16
php.ini used:	/usr/local/php8.1/conf/php.ini
MySQL binary:	/usr/bin/mysql
MySQL version:	mysql  Ver 15.1 Distrib 10.5.18-MariaDB, for debian-linux-gnu (x86_64) using  EditLine wrapper
SQL modes:	ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
WP-CLI root dir:	phar://wp-cli.phar/vendor/wp-cli/wp-cli
WP-CLI vendor dir:	phar://wp-cli.phar/vendor
WP_CLI phar path:	/chroot/var/www
WP-CLI packages dir:	
WP-CLI global config:	
WP-CLI project config:	
WP-CLI version:	2.6.0

Provide a possible solution

Plenty of variations:

$before_caps = $before[ $role_key ] ? $before[ $role_key ]->capabilities : [];
$restored_cap = array_diff_key( $after[ $role_key ]->capabilities, $before_caps );
$removed_cap  = array_diff_key( $before_caps, $after[ $role_key ]->capabilities );