The `$credentials['user_login']` and `$credentials['user_password']` parameters are passed by reference to the `wp_authenticate` action, and are at that point [https://www.php.net/manual/en/language.references.pass.php#124383 created as null] if they don't exist in the array.

This commit sets those values to an empty string, resolving two PHP 8.1 deprecation notices:
 * One from `preg_replace()` in `wp_strip_all_tags()` via `sanitize_user()` in `wp_authenticate()`:
{{{
Deprecated: preg_replace(): Passing null to parameter WordPress#3 ($subject) of type array|string is deprecated
}}}
 * One from `trim()` in `wp_authenticate()` itself:
{{{
Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated
}}}

Includes documenting the `$credentials` parameter using hash notation.

Follow-up to [6643], [37697].

Props lenasterg, TobiasBg, ocean90, afragen, lkraav, SergeyBiryukov.
Fixes #56850.

git-svn-id: https://develop.svn.wordpress.org/trunk@55301 602fd350-edb4-49c9-b593-d223f7449a82

…air screen.

The table is no longer created by core as of WordPress 3.0, and support for global terms was removed in WordPress 6.1, so `$wpdb->sitecategories` is unset by default.

This commit resolves a "passing null to non-nullable" deprecation notice on PHP 8.1:
{{{
Deprecated: addcslashes(): Passing null to parameter #1 ($string) of type string is deprecated in wp-includes/class-wpdb.php on line 1804
}}}

The `tables_to_repair` filter is available for plugins to readd the table or include any additional tables to repair.

Follow-up to [14854], [14880], [54240].

Props ipajen, chiragrathod103, SergeyBiryukov.
Fixes #57762.

git-svn-id: https://develop.svn.wordpress.org/trunk@55421 602fd350-edb4-49c9-b593-d223f7449a82