Preview button broken with custom post types (fix attached)

The preview button for custom post types was broken in the metabox and elsewhere. This is the fix that worked for us:]

--- a/wp-content/plugins/wp-permastructure/wp-permastructure.php
+++ b/wp-content/plugins/wp-permastructure/wp-permastructure.php
@@ -334,7 +334,7 @@ class wp_permastructure {
                        $permalink = home_url( str_replace($rewritecode, $rewritereplace, $permalink) );
                        $permalink = user_trailingslashit($permalink, 'single');
                } else { // if they're not using the fancy permalink option
-                       $permalink = home_url('?p=' . $post->ID);
+                       $permalink = $post_link ? $post_link : home_url('?p=' . $post->ID);
                }
 
                return $permalink;