fix nil commentary case for pixiv strategy #3948

app/logical/sources/strategies/pixiv.rb

@@ -26,6 +26,10 @@ module Sources
       end
 
       def self.to_dtext(text)
+        if text.nil?
+          return nil
+        end
+        
         text = text.gsub(%r!https?://www\.pixiv\.net/member_illust\.php\?mode=medium&illust_id=([0-9]+)!i) do |match|
           pixiv_id = $1
           %(pixiv ##{pixiv_id} "»":[/posts?tags=pixiv:#{pixiv_id}])