Added the 'user_data' key to the userdata property so that sessions using a database can be deleted properly when using the table schema found in the "Saving Session Data to a Database" section of the Session Class in the user guide.
diff --git a/system/libraries/Session.php b/system/libraries/Session.php
index 2c8a801..8ee08c5 100644
--- a/system/libraries/Session.php
+++ b/system/libraries/Session.php
@@ -317,7 +317,8 @@
 							'session_id'	=> md5(uniqid($sessid, TRUE)),
 							'ip_address'	=> $this->CI->input->ip_address(),
 							'user_agent'	=> substr($this->CI->input->user_agent(), 0, 120),
-							'last_activity'	=> $this->now
+							'last_activity'	=> $this->now,
+							'user_data'		=> ''
 							);