```ruby
class DiscussionSerializer < ApplicationSerializer
  include ReadraptorTrackable
  include MarkdownHelper

  attributes :number, :title, :url, :description_html, :comments_count

  def url
    product_discussion_path(product, number)
  end

  def product
    @product ||= object.product
  end

  def description_html
    product_markdown(product, object.comments.first.body)
  end
end
```

Fix 500 errors with some discussions
user
```ruby
class DiscussionSerializer < ApplicationSerializer
  include ReadraptorTrackable
  include MarkdownHelper

  attributes :number, :title, :url, :description_html, :comments_count

  def url
    product_discussion_path(product, number)
  end

  def product
    @product ||= object.product
  end

  def description_html
    product_markdown(product, object.comments.first.try(:body))
  end
end
```
assistant