```ruby
require 'devise_zxcvbn/email_tokeniser'

module Devise
  module Models
    module Zxcvbnable
      extend ActiveSupport::Concern

      delegate :min_password_score, to: "self.class"

      included do
        validate :not_weak_password, if: :password_required?
      end

      private

      def not_weak_password
        weak_words = [self.email] + DeviseZxcvbn::EmailTokeniser.split(self.email)
        password_score = ::Zxcvbn.test(password, weak_words).score
        if password_score < min_password_score
          self.errors.add :password, :weak_password, score: password_score, min_password_score: min_password_score
          return false
        end
      end

      module ClassMethods
        Devise::Models.config(self, :min_password_score)
      end
    end
  end
end```

Add email (and tokenized email parts) to dictionary only when non-nil
user
```ruby
require 'devise_zxcvbn/email_tokeniser'

module Devise
  module Models
    module Zxcvbnable
      extend ActiveSupport::Concern

      delegate :min_password_score, to: "self.class"

      included do
        validate :not_weak_password, if: :password_required?
      end

      private

      def not_weak_password
        weak_words = if self.email
          [self.email, *DeviseZxcvbn::EmailTokeniser.split(self.email)]
        else
          []
        end

        password_score = ::Zxcvbn.test(password, weak_words).score
        if password_score < min_password_score
          self.errors.add :password, :weak_password, score: password_score, min_password_score: min_password_score
          return false
        end
      end

      module ClassMethods
        Devise::Models.config(self, :min_password_score)
      end
    end
  end
end
```
assistant