firefox 20.0.1 NS_ERROR_UNEXPECTED: Unexpected error @ underscore.string/dist/underscore.string.js:883

firefox 20.0.1
NS_ERROR_UNEXPECTED: Unexpected error @ underscore.string/dist/underscore.string.js:883
line var val = global.localStorage[name];?

code
function config (name) {
// accessing global.localStorage can trigger a DOMException in sandboxed iframes
try {
if (!global.localStorage) return false;
} catch (_) {
return false;
}
var val = global.localStorage[name];
if (null == val) return false;
return String(val).toLowerCase() === 'true';
}