Merge 3.9 RC5 fixes into master (#6459)

* UI fixes for 3.9 (#6400)

* UI fixes for header icon alignment

* PLT-6569 - Fixing pin icon in header

* PLT-6505 - Updating z-index for emoji picker

* Updating z-index for overlaying sidebar

* PLT-6134 - Fix for emoji picker on comments

* Reverting emoji picker fix

* Fixing alignment for header icons

* Removing channel title changes

* Don't show mention badge for active channel (#6411)

* PLT-6583 - Fixing RHS compact view (#6413)

webapp/stores/channel_store.jsx

@@ -560,7 +560,9 @@ ChannelStore.dispatchToken = AppDispatcher.register((payload) => {
         var markRead = id === ChannelStore.getCurrentId() && window.isActive;
 
         if (TeamStore.getCurrentId() === teamId || teamId === '') {
-            ChannelStore.incrementMentionsIfNeeded(id, action.websocketMessageProps);
+            if (!markRead) {
+                ChannelStore.incrementMentionsIfNeeded(id, action.websocketMessageProps);
+            }
             ChannelStore.incrementMessages(id, markRead);
         }
         break;