```ruby
class Proposition < ActiveRecord::Base
  attr_accessible :description, :on_behalf_of, :body, :representative_id

  belongs_to :vote
  belongs_to :representative

  alias_method :delivered_by, :representative

  validates_presence_of :body
  validates_uniqueness_of :external_id

  def plain_body
    Nokogiri::HTML.parse(body).inner_text.strip
  end

  def short_body
    str = plain_body
    str.size <= 200 ? str : "#{str[0,197]}..."
  end
end
```

Allow nil external_id on Proposition.
user
```ruby
class Proposition < ActiveRecord::Base
  attr_accessible :description, :on_behalf_of, :body, :representative_id

  belongs_to :vote
  belongs_to :representative

  alias_method :delivered_by, :representative

  validates_presence_of :body
  validates_uniqueness_of :external_id, allow_nil: true # https://github.com/holderdeord/hdo-site/issues/138

  def plain_body
    Nokogiri::HTML.parse(body).inner_text.strip
  end

  def short_body
    str = plain_body
    str.size <= 200 ? str : "#{str[0,197]}..."
  end
end
```
assistant