undefined method `donation_interests?' for nil:NilClass, multiply checkbox

I try to design the check box for the donation_interest but I don't know why I get this error? I will appreciate if you can help me.

module DonorProfilesHelper
  def checked(area)
     @donor_profiles.donation_interests.nil? ? false: @donor_profiles.donation_interests.match(area)
   end  
end

class DonorProfilesController < ApplicationController

  def donor_profile_params
    params.require(:donor_profile).permit(:first_name, :last_name, :description,
                                            :date_created, :address, :phone_number,
                                            :email,:sort_type, 
                                            donations_attributes: [:amount, :created_at],donation_interests:[])
  end

routes.rb

Rails.application.routes.draw do
  resources :donor_profiles

  get 'password_resets/new'

  get 'password_resets/edit'

  get 'sessions/new'

  root                  'static_pages#home'
  get     'donors'  =>  'donor_profiles#index'

donor_profile.rb

class DonorProfile < ActiveRecord::Base

    attr_accessor :donations_attributes
    has_many :donations
    accepts_nested_attributes_for :donations
    scope :donation_interests, -> donation_interests { where donation_interests: donation_interests }    
    def fullname
      "#{first_name} #{last_name}"
    end
      before_save do
        self.donation_interests.gsub!(/[\[\]\"]/,"") if attribute_present?("donation_interests")
      end
end