Docs: Clarify that the $wp_error parameter of login_header() is n…

…ullable.

Follow-up to [7991], [25701], [28792], [43457], [58209], [58220].

See #60668, #60699.

git-svn-id: https://develop.svn.wordpress.org/trunk@58224 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-login.php

@@ -33,10 +33,10 @@
  *                                    upon successful login.
  * @global string      $action        The action that brought the visitor to the login page.
  *
- * @param null|string $title    Optional. WordPress login Page title to display in the `<title>` element.
- *                              Default null, which displays 'Log In'.
- * @param string      $message  Optional. Message to display in header. Default empty.
- * @param WP_Error    $wp_error Optional. The error to pass. Default is a WP_Error instance.
+ * @param string|null   $title    Optional. WordPress login page title to display in the `<title>` element.
+ *                                Defaults to 'Log In'.
+ * @param string        $message  Optional. Message to display in header. Default empty.
+ * @param WP_Error|null $wp_error Optional. The error to pass. Defaults to a WP_Error instance.
  */
 function login_header( $title = null, $message = '', $wp_error = null ) {
 	global $error, $interim_login, $action;