Nil values on enums fails to authorize

[patodevilla]

Steps to reproduce

Adding a can rule to authorize when a value is nil fails to authorize.

class Person < ActiveRecord::Base
  enum my_enum: {
    'something' => 0,
    'other' => 1
  }
end

class TestAbility
  include CanCan::Ability

  def initialize
    # can [:create], Person, my_enum: nil # also fails
    can [:create], Person, my_enum: [nil]
  end
end

TestAbility.new().can? :create, Person.new()

The bug is caused by this line because nil becomes ''

This would fix it

array_values = Array(value).map{|v| v.nil? ? nil : v.to_s }
!(array_values & [attribute, raw_attribute]).empty?

Expected behavior

Should return true

Actual behavior

Returns false

System configuration

Rails version:
6.1.0

Ruby version:
2.7.4

CanCanCan version
3.2.0