fix author join for federation callbacks with Poll

app/models/poll.rb

@@ -5,12 +5,13 @@ class Poll < ActiveRecord::Base
   belongs_to :status_message
   has_many :poll_answers, -> { order 'id ASC' }
   has_many :poll_participations
+  has_one :author, through: :status_message
 
   xml_attr :question
   xml_attr :poll_answers, :as => [PollAnswer]
 
   #forward some requests to status message, because a poll is just attached to a status message and is not sharable itself
-  delegate :author, :author_id, :diaspora_handle, :public?, :subscribers, to: :status_message
+  delegate :author_id, :diaspora_handle, :public?, :subscribers, to: :status_message
 
   validate :enough_poll_answers
   validates :question, presence: true