Merge pull request #586 from blasto333/develop

Check for string value before doing str_replace. (Issue #439)
diff --git a/user_guide_src/source/libraries/sessions.rst b/user_guide_src/source/libraries/sessions.rst
index ef32f5d..89c64fd 100644
--- a/user_guide_src/source/libraries/sessions.rst
+++ b/user_guide_src/source/libraries/sessions.rst
@@ -242,7 +242,7 @@
 	CREATE TABLE IF NOT EXISTS  `ci_sessions` (
 		session_id varchar(40) DEFAULT '0' NOT NULL,
 		ip_address varchar(16) DEFAULT '0' NOT NULL,
-		user_agent varchar(120) NOT NULL,
+		user_agent varchar(255) NOT NULL,
 		last_activity int(10) unsigned DEFAULT 0 NOT NULL,
 		user_data text NOT NULL,
 		PRIMARY KEY (session_id),