Ticket #15959: get_adjacent_post.2.patch

wp-includes/link-template.php

@@ -1103 +1103 @@
         if ( empty( $post ) )
                 return null;
 
+        $post_category_count = count( wp_get_post_categories( $post->ID ) );
+        if ( $in_same_cat && ! $post_category_count )
+                return null;
+        
+        if ( !$post_category_count )
+                $in_same_cat = false;
+
         $current_post_date = $post->post_date;
 
         $join = '';