Properly checked for channel change before closing LHS (#2833)

webapp/components/sidebar.jsx

@@ -162,7 +162,7 @@ export default class Sidebar extends React.Component {
         }
         return false;
     }
-    componentDidUpdate() {
+    componentDidUpdate(prevProps, prevState) {
         this.updateTitle();
         this.updateUnreadIndicators();
         if (!Utils.isMobile()) {
@@ -170,9 +170,11 @@ export default class Sidebar extends React.Component {
         }
 
         // close the LHS on mobile when you change channels
+        if (this.state.activeId !== prevState.activeId) {
             $('.app__body .inner-wrap').removeClass('move--right');
             $('.app__body .sidebar--left').removeClass('move--right');
         }
+    }
     componentWillUnmount() {
         window.removeEventListener('resize', this.handleResize);