Fix missing element in for wp_mail_succeeded filter

Author: iFlair

src/wp-includes/pluggable.php

@@ -618,7 +618,7 @@ function wp_mail( $to, $subject, $message, $headers = '', $attachments = array()
 		 */
 		do_action_ref_array( 'phpmailer_init', array( &$phpmailer ) );
 
-		$mail_data = compact( 'to', 'subject', 'message', 'headers', 'attachments' );
+		$mail_data = compact( 'to', 'subject', 'message', 'headers', 'attachments', 'embeds' );
 
 		// Send!
 		try {