Ticket #22271: 22271.diff

diff --git wp-includes/post-template.php wp-includes/post-template.php
index a8e4f89..6a26d80 100644
--- wp-includes/post-template.php
+++ wp-includes/post-template.php
@@ -318,6 +318,12 @@ function get_post_class( $class = '', $post_id = null ) {
 
        $classes = array();
 
+       if ( !empty($class) ) {
+               if ( !is_array( $class ) )
+                       $class = preg_split('#\s+#', $class);
+               $classes = array_merge($classes, $class);
+       }
+
        if ( empty($post) )
                return $classes;
 
@@ -366,12 +372,6 @@ function get_post_class( $class = '', $post_id = null ) {
                }
        }
 
-       if ( !empty($class) ) {
-               if ( !is_array( $class ) )
-                       $class = preg_split('#\s+#', $class);
-               $classes = array_merge($classes, $class);
-       }
-
        $classes = array_map('esc_attr', $classes);
 
        return apply_filters('post_class', $classes, $class, $post->ID);