Media: Prevent PHP notice in `get_avatar()`.

Follow up fix to [56690].

Props pereirinha, mukesh27, spacedmonkey.
Fixes #58892.

Built from https://develop.svn.wordpress.org/trunk@56756


git-svn-id: http://core.svn.wordpress.org/trunk@56268 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/pluggable.php

@@ -2845,6 +2845,7 @@ if ( ! function_exists( 'get_avatar' ) ) :
 			'loading'       => null,
 			'fetchpriority' => null,
 			'extra_attr'    => '',
+			'decoding'      => null,
 		);
 
 		if ( empty( $args ) ) {

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.4-beta1-56755';
+$wp_version = '6.4-beta1-56756';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.