Index: src/wp-includes/author-template.php
===================================================================
--- src/wp-includes/author-template.php	(revision 55744)
+++ src/wp-includes/author-template.php	(working copy)
@@ -14,11 +14,12 @@
  * Retrieves the author of the current post.
  *
  * @since 1.5.0
+ * @since 6.3.0 Returns an empty string if the author's display name is unknown.
  *
  * @global WP_User $authordata The current author's data.
  *
  * @param string $deprecated Deprecated.
- * @return string|null The author's display name.
+ * @return string The author's display name, empty string if unknown.
  */
 function get_the_author( $deprecated = '' ) {
 	global $authordata;
@@ -32,9 +33,9 @@
 	 *
 	 * @since 2.9.0
 	 *
-	 * @param string|null $display_name The author's display name.
+	 * @param string $display_name The author's display name.
 	 */
-	return apply_filters( 'the_author', is_object( $authordata ) ? $authordata->display_name : null );
+	return apply_filters( 'the_author', is_object( $authordata ) ? $authordata->display_name : '' );
 }
 
 /**
@@ -55,7 +56,7 @@
  *
  * @param string $deprecated      Deprecated.
  * @param bool   $deprecated_echo Deprecated. Use get_the_author(). Echo the string or return it.
- * @return string|null The author's display name, from get_the_author().
+ * @return string The author's display name, from get_the_author().
  */
 function the_author( $deprecated = '', $deprecated_echo = true ) {
 	if ( ! empty( $deprecated ) ) {
@@ -226,8 +227,8 @@
  *
  * @global WP_User $authordata The current author's data.
  *
- * @return string|null An HTML link if the author's url exist in user meta,
- *                     else the result of get_the_author().
+ * @return string An HTML link if the author's url exist in user meta,
+ *                else the result of get_the_author().
  */
 function get_the_author_link() {
 	if ( get_the_author_meta( 'url' ) ) {