Fix LoadMore on account media gallery (#6933)

max_id in the fetch request should be a status id, but media attachment id was used.

app/javascript/mastodon/features/account_gallery/index.js

@@ -67,7 +67,7 @@ export default class AccountGallery extends ImmutablePureComponent {
 
   handleScrollToBottom = () => {
     if (this.props.hasMore) {
-      this.handleLoadMore(this.props.medias.last().get('id'));
+      this.handleLoadMore(this.props.medias.last().getIn(['status', 'id']));
     }
   }