Check if we have already narrowed to a stream.

While narrowing, we should check if we have already narrowed to the
required stream.

Author: Sam1301

app/src/main/java/com/zulip/android/activities/ZulipActivity.java

@@ -1884,8 +1884,9 @@ public void onNarrow(NarrowFilter narrowFilter) {
 
 
     public void onNarrow(NarrowFilter narrowFilter, int messageId) {
-        // TODO: check if already narrowed to this particular stream/subject
-        doNarrow(narrowFilter, messageId);
+        if (narrowedList == null || narrowFilter != narrowedList.filter) {
+            doNarrow(narrowFilter, messageId);
+        }
     }
 
     @Override