[misc] modification for mobile (#4016)

frontend/src/components/toolbar/invitations-toolbar.js

@@ -1,9 +1,9 @@
 import React from 'react';
 import PropTypes from 'prop-types';
-import MediaQuery from 'react-responsive';
 import CommonToolbar from './common-toolbar';
 import { Button } from 'reactstrap';
 import { gettext } from '../../utils/constants';
+import { Utils } from '../../utils/utils';
 
 const propTypes = {
   onShowSidePanel: PropTypes.func.isRequired,
@@ -24,7 +24,7 @@ class InvitationsToolbar extends React.Component {
         <div className="cur-view-toolbar">
           <span title="Side Nav Menu" onClick={onShowSidePanel} className="sf2-icon-menu side-nav-toggle hidden-md-up d-md-none">
           </span>
-          {window.innerWidth >= 768 ? (
+          {Utils.isDesktop() ? (
             <div className="operation">
               <Button color="btn btn-secondary operation-item" onClick={toggleInvitePeopleDialog}>
                 <i className="fas fa-plus-square text-secondary mr-1"></i>{gettext('Invite People')}