Don't try loading embeds on deleted topics

app/jobs/regular/crawl_topic_link.rb

@@ -88,7 +88,8 @@ module Jobs
 
       # Look for a topic embed for the URL. If it exists, use its title and don't crawl
       topic_embed = TopicEmbed.where(embed_url: topic_link.url).includes(:topic).references(:topic).first
-      if topic_embed.present?
+      # topic could be deleted, so skip
+      if topic_embed && topic_embed.topic
         TopicLink.where(id: topic_link.id).update_all(['title = ?, crawled_at = CURRENT_TIMESTAMP', topic_embed.topic.title[0..255]])
         return
       end