(MAINT) Ensure is_same check works for nil manifest values

[bwilcox]

When working with networkingdsc and using dsc_firewall we encounted an issue where the code attempts to sort a nil value:

 C:\Users\Administrator\test\modules\networkingdsc> puppet apply .\examples\test.pp --modulepath .\spec\fixtures\modules\
Notice: Compiled catalog for lay-escalation.delivery.puppetlabs.net in environment production in 0.21 seconds
Error: undefined method `sort' for nil:NilClass
PS C:\Users\Administrator\test\modules\networkingdsc>

Using pry I can see the offending parameter:

From: C:/Users/Administrator/test/modules/networkingdsc/spec/fixtures/modules/pwshlib/lib/puppet/provider/dsc_base_provider/dsc_base_provider.rb @ line 66 Puppet::Provider::DscBaseProvider#canonicalize:

    61:           end
    62:           downcased_result = recursively_downcase(canonicalized)
    63:           downcased_resource = recursively_downcase(r)
    64:           downcased_result.each do |key, value|
    65:             #is_same = (value.is_a?(Enumerable) & !downcased_resource[key].nil?) ? downcased_resource[key].sort == value.sort : downcased_resource[key] == value
 => 66:             is_same = value.is_a?(Enumerable) ? downcased_resource[key].sort == value.sort : downcased_resource[key] == value
    67:                         canonicalized[key] = r[key] unless is_same
    68:             canonicalized.delete(key) unless downcased_resource.keys.include?(key)
    69:           end
    70:           # Cache the actually canonicalized resource separately
    71:           @@cached_canonicalized_resource << canonicalized.dup
[26] pry(#<Puppet::Provider::DscFirewall::DscFirewall>)> key
=> :dsc_localport
[27] pry(#<Puppet::Provider::DscFirewall::DscFirewall>)> value
=> ["any"]
[28] pry(#<Puppet::Provider::DscFirewall::DscFirewall>)> downcased_resource[key]
=> nil
[29] pry(#<Puppet::Provider::DscFirewall::DscFirewall>)> next

From: C:/Ruby25-x64/lib/ruby/gems/2.5.0/gems/puppet-7.3.0-x64-mingw32/lib/puppet/application/apply.rb @ line 264 Puppet::Application::Apply#main:

    259:           exit(exit_status)
    260:         else
    261:           exit(0)
    262:         end
    263:       rescue => detail
 => 264:         Puppet.log_exception(detail)
    265:         exit(1)
    266:       end
    267:     end
    268:   end
    269:
[29] pry(#<Puppet::Application::Apply>)>

This request adds a check for nil values. I'm not sure if this is the best way to solve the problem, but in my continued testing it does the job.