fix errors

app/logical/sources/site.rb

@@ -7,7 +7,7 @@ module Sources
       :profile_url, :image_url, :tags, :artist_record, :unique_id, 
       :page_count, :file_url, :ugoira_frame_data, :image_urls, 
       :has_artist_commentary?, :artist_commentary_title,
-      :artist_commentary_desc, :referer_url, :to => :strategy
+      :artist_commentary_desc, :to => :strategy
 
     def self.strategies
       [Strategies::Pixiv, Strategies::NicoSeiga, Strategies::DeviantArt, Strategies::Nijie, Strategies::Twitter]
@@ -24,6 +24,10 @@ module Sources
       end
     end
 
+    def referer_url
+      strategy.try(:referer_url)
+    end
+
     def normalized_for_artist_finder?
       available? && strategy.normalized_for_artist_finder?
     end

app/logical/sources/strategies/base.rb

@@ -9,7 +9,7 @@ module Sources
         false
       end
 
-      def initialize(url, referer_url)
+      def initialize(url, referer_url = nil)
         @url = url
         @referer_url = referer_url
         @page_count = 1