fix an error in ie8

JS Error: transform.js() is not a function (IE8) - https://my.trackjs.com/details/cc1a98ca1dce4a28ac40461d8911c8bf
https://trello.com/c/YbZQ7Z6R/204-js-error-transform-js-is-not-a-function-ie8-https-my-trackjs-com-details-cc1a98ca1dce4a28ac40461d8911c8bf