fix share intent. (#4926)

app/javascript/mastodon/features/standalone/compose/index.js

@@ -2,6 +2,7 @@ import React from 'react';
 import ComposeFormContainer from '../../compose/containers/compose_form_container';
 import NotificationsContainer from '../../ui/containers/notifications_container';
 import LoadingBarContainer from '../../ui/containers/loading_bar_container';
+import ModalContainer from '../../ui/containers/modal_container';
 
 export default class Compose extends React.PureComponent {
 
@@ -10,6 +11,7 @@ export default class Compose extends React.PureComponent {
       <div>
         <ComposeFormContainer />
         <NotificationsContainer />
+        <ModalContainer />
         <LoadingBarContainer className='loading-bar' />
       </div>
     );