When a poll is created, and any of the questions for that poll doesn't
have any answer created, the following exception was raised when
trying to see the results:
Failure/Error: question_answers.max_by {|answer| answer.total_votes }.id
ActionView::Template::Error:
undefined method `id' for nil:NilClass
./app/models/poll/question.rb:66:in `most_voted_answer_id'