Hide some components rather than unmounting (#2271)

Hide some components rather than unmounting them to allow to show again
quickly and keep the view state such as the scrolled offset.

app/assets/javascripts/components/features/community_timeline/index.jsx

@@ -77,7 +77,7 @@ class CommunityTimeline extends React.PureComponent {
     return (
       <Column icon='users' active={hasUnread} heading={intl.formatMessage(messages.title)}>
         <ColumnBackButtonSlim />
-        <StatusListContainer type='community' emptyMessage={<FormattedMessage id='empty_column.community' defaultMessage='The local timeline is empty. Write something publicly to get the ball rolling!' />} />
+        <StatusListContainer {...this.props} scrollKey='community_timeline' type='community' emptyMessage={<FormattedMessage id='empty_column.community' defaultMessage='The local timeline is empty. Write something publicly to get the ball rolling!' />} />
       </Column>
     );
   }