Add import { Cookies } to fileUpload.js.

lib/fileUpload.js

@@ -2,6 +2,7 @@
 
 if (UploadFS) {
 	const initFileStore = function() {
+		import { Cookies } from 'meteor/ostrio:cookies';
 		const cookie = new Cookies();
 		if (Meteor.isClient) {
 			document.cookie = 'rc_uid=' + escape(Meteor.userId()) + '; path=/';