Preserve ConversationList scroll state in between onPause/onResume.

src/org/thoughtcrime/securesms/ConversationListFragment.java

@@ -100,9 +100,11 @@ public class ConversationListFragment extends SherlockListFragment
   }
 
   public void setMasterSecret(MasterSecret masterSecret) {
+    if (this.masterSecret != masterSecret) {
       this.masterSecret = masterSecret;
       initializeListAdapter();
     }
+  }
 
   @SuppressLint({ "NewApi", "NewApi" })
   private void initializeSearch(android.widget.SearchView searchView) {