Bail early when invalid ID is passed to `get_comment_class()`.

This helps to avoid PHP notices later in the function.

Props walterebert, dipesh.kakadiya, DrewAPicture.
Fixes #33947.
Built from https://develop.svn.wordpress.org/trunk@34454


git-svn-id: http://core.svn.wordpress.org/trunk@34418 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/comment-template.php

@@ -433,10 +433,13 @@ function comment_class( $class = '', $comment = null, $post_id = null, $echo = t
 function get_comment_class( $class = '', $comment_id = null, $post_id = null ) {
 	global $comment_alt, $comment_depth, $comment_thread_alt;
 
-	$comment = get_comment($comment_id);
-
 	$classes = array();
 
+	$comment = get_comment( $comment_id );
+	if ( ! $comment ) {
+		return $classes;
+	}
+
 	// Get the comment type (comment, trackback),
 	$classes[] = ( empty( $comment->comment_type ) ) ? 'comment' : $comment->comment_type;
 

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-alpha-34453';
+$wp_version = '4.4-alpha-34454';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.