remove bug if timeZone is not found, set default timeTimeZone as empty s...

If timeZone is not found, there are error like: "Undefined variable: timezone in file "/var/www/20141219141026/vendor/geoip/geoip/src/timezone.php" on line "2234". 
For fix this bug, i set default timeZone as NULL. So if the timezone is not found, returns NULL.