Fix util.js warn function to not blow up IE11
Fix util.js warn function to not blow up IE11

It was called with a null which was causing a problem on IE11
i18next/react-i18next,i18next/react-i18next,i18next/react-i18next,i18next/react-i18next,i18next/react-i18next,i18next/react-i18next,i18next/react-i18next,i18next/react-i18next