undefined method key?' for nil:NilClass when AllCops` is empty

[volmer]

With the following content on rubocop.yml

AllCops:

RuboCop explodes:

undefined method `key?' for nil:NilClass
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/rubocop-0.36.0/lib/rubocop/config.rb:241:in `check_obsolete_parameter'
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/rubocop-0.36.0/lib/rubocop/config.rb:235:in `reject_obsolete_parameters'
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/rubocop-0.36.0/lib/rubocop/config.rb:114:in `validate'
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/rubocop-0.36.0/lib/rubocop/config_loader.rb:48:in `load_file'
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/rubocop-0.36.0/lib/rubocop/config_loader.rb:96:in `configuration_from_file'
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/rubocop-0.36.0/lib/rubocop/config_store.rb:41:in `for'
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/rubocop-0.36.0/lib/rubocop/cli.rb:88:in `apply_default_formatter'
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/rubocop-0.36.0/lib/rubocop/cli.rb:26:in `run'
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/rubocop-0.36.0/bin/rubocop:14:in `block in <top (required)>'
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/2.3.0/benchmark.rb:308:in `realtime'
/Users/volmer/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/gems/rubocop-0.36.0/bin/rubocop:13:in `<top (required)>'
/Users/volmer/.rbenv/versions/2.3.0/bin/rubocop:23:in `load'
/Users/volmer/.rbenv/versions/2.3.0/bin/rubocop:23:in `<main>'

I think instead it should raise RuboCop::ValidationError complaining about the empty config, or maybe just ignore AllCops altogether.