FIX: missing avatar when sizing down window

app/assets/stylesheets/desktop/topic-list.scss

@@ -123,7 +123,7 @@
     }
   }
   .avatar {
-    &.latest {
+    &.latest:not(.single) {
       @include box-shadow(0 0 6px 1px desaturate(scale-color($tertiary, $lightness: 30%), 35%));
     }
   }

app/models/topic_posters_summary.rb

@@ -16,7 +16,10 @@ class TopicPostersSummary
     TopicPoster.new.tap do |topic_poster|
       topic_poster.user = user
       topic_poster.description = descriptions_for(user)
-      topic_poster.extras = 'latest' if include_latest_class?(user)
+      if topic.last_post_user_id == user.id
+        topic_poster.extras = 'latest'
+        topic_poster.extras << ' single' if user_ids.uniq.size == 1
+      end
     end
   end
 
@@ -29,10 +32,6 @@ class TopicPostersSummary
     end
   end
 
-  def include_latest_class?(user)
-    topic.last_post_user_id == user.id && user_ids.uniq.size > 1
-  end
-
   def descriptions_for(user)
     descriptions_by_id[user.id].join ', '
   end