Backport #91

Author: STRML

lib/utils/getPrefix.es6

@@ -9,5 +9,6 @@ export default (function() {
       )[1];
   // 'ms' is not titlecased
   if (pre === 'ms') return pre;
+  if (pre === undefined || pre === null) return '';
   return pre.slice(0, 1).toUpperCase() + pre.slice(1);
 })();