Fixed return values types in session drivers
diff --git a/system/libraries/Session/drivers/Session_redis_driver.php b/system/libraries/Session/drivers/Session_redis_driver.php
index c3c75b3..af427d2 100644
--- a/system/libraries/Session/drivers/Session_redis_driver.php
+++ b/system/libraries/Session/drivers/Session_redis_driver.php
@@ -171,7 +171,7 @@
 			return $session_data;
 		}
 
-		return FALSE;
+		return '';
 	}
 
 	// ------------------------------------------------------------------------