FIX: onebox local topic when using slug-less URL

When linking to a topic in the same Discourse, we try to onebox the link to show the title
and other various information depending on whether it's a "standard" or "inline" onebox.

However, we were not properly detecting links to topics that had no slugs (eg. https://meta.discourse.org/t/1234).

lib/oneboxer.rb

@@ -219,9 +219,7 @@ module Oneboxer
       end
     end
 
-    topic = Topic.find_by(id: route[:topic_id])
-
-    return unless topic
+    return unless topic = Topic.find_by(id: route[:id] || route[:topic_id])
     return if topic.private_message?
 
     if current_category.blank? || current_category.id != topic.category_id