default value of $total_rows in Pagination class should be number. And fix User Guide Pagination Class's Example which uses string to number variable.
diff --git a/system/libraries/Pagination.php b/system/libraries/Pagination.php
index 1113f86..cc62e66 100644
--- a/system/libraries/Pagination.php
+++ b/system/libraries/Pagination.php
@@ -30,7 +30,7 @@
var $prefix = ''; // A custom prefix added to the path.
var $suffix = ''; // A custom suffix added to the path.
- var $total_rows = ''; // Total number of items (database results)
+ var $total_rows = 0; // Total number of items (database results)
var $per_page = 10; // Max number of items you want shown per page
var $num_links = 2; // Number of "digit" links to show before/after the currently viewed page
var $cur_page = 0; // The current page being viewed