Form item disappearing when failing nested validations

class BooksController < ApplicationController

  ...


def new

    @book = Book.new

    @book.authors.build

  end

def create

    @book = current_user.books.create(book_params)

    params[:book][:authors_attributes].each do |k,v|

      author = Author.find_or_create_by(name: v['name'], user_id: current_user.id)

      @book.book_authors.build(author_id: author.id)

    end

if @book.save
    redirect_to book_path(@book)
else
  render :new
end


end

private

def book_params

    params.require(:book).permit(:title, :published_city, :description, author_ids:[])

  end

def author_params

    params.require(:book).permit(authors_attributes: [:id, :name, :_destroy])

  end

end

class Book < ApplicationRecord


has_many :book_authors

  has_many :authors, through: :book_authors

  belongs_to :user

accepts_nested_attributes_for :authors, allow_destroy: true

  validates :title, :published_city, presence: true

  validates_associated :authors, inverse_of: :book

end

class BookAuthor < ApplicationRecord

  belongs_to :book

  belongs_to :author

end

class Author < ApplicationRecord

  has_many :book_authors

  has_many :books, through: :book_authors


validates :name, presence: true

end

<%= form_for @book do |f| %>

  <%= f.text_field :title, required: true %>

  <%= f.text_area :description %>

  <div id='authors'>

    <%= f.fields_for :authors do |author| %>

      <%= render 'author_fields', :f => author %>

    <% end %>

    <div class='links'>

      <%= link_to_add_association 'Add another author', f, :authors %>

    </div>

  </div>

  <%= f.text_field :published_city %>

  <%= f.submit %>

<% end %>