Perform the where(...).first to find_by(...) refactoring.

This refactoring was automated using the command: bundle exec "ruby refactorings/where_dot_first_to_find_by/app.rb"

app/models/topic_link_click.rb

@@ -33,7 +33,7 @@ class TopicLinkClick < ActiveRecord::Base
 
       # If we have it somewhere else on the site, just allow the redirect. This is
       # likely due to a onebox of another topic.
-      link = TopicLink.where(url: args[:url]).first
+      link = TopicLink.find_by(url: args[:url])
       return link.present? ? link.url : nil
     end