[ci skip] Add some 'debug' log messages to CI_Session
diff --git a/system/libraries/Session/Session.php b/system/libraries/Session/Session.php
index c9d2e8a..1bdc6e5 100644
--- a/system/libraries/Session/Session.php
+++ b/system/libraries/Session/Session.php
@@ -91,6 +91,7 @@
 		// Note: BC workaround
 		elseif (config_item('sess_use_database'))
 		{
+			log_message('debug', 'Session: "sess_driver" is empty; using BC fallback to "sess_use_database".');
 			$this->_driver = 'database';
 		}