Fix undefined method error in sidekiq (#9807)

* Fix undefined method error in sidekiq

Body can be not nil but still be empty, which causes a
`NoMethodError: undefined method `[]' for nil:NilClass` further in the
code. This checks for an empty body to avoid the issue.

* Fix codeclimate issue

app/services/fetch_oembed_service.rb

@@ -43,7 +43,7 @@ class FetchOEmbedService
       res.code != 200 ? nil : res.body_with_limit
     end
 
-    validate(parse_for_format(body)) unless body.nil?
+    validate(parse_for_format(body)) if body.present?
   rescue Oj::ParseError, Ox::ParseError
     nil
   end