Specifying blacklist_keys with whitelist_keys can result in error

[thompiler]

Specifying both blacklist_keys and whitelist_keys, can result in an error.

Example Airbrake config:

Airbrake.configure do |c|
  ...

  c.blacklist_keys = %i[password password_confirmation]
  c.whitelist_keys = [:email, /user/i, 'account_id']
end

(commenting out the blacklist_keys line or setting blacklist_keys = [] does not result in this error)

Error shown in log:

NoMethodError (undefined method `each_key' for "[Filtered]":String
Did you mean?  each_byte):
  airbrake-ruby (2.5.0) lib/airbrake-ruby/filters/keys_filter.rb:76:in `filter_hash'
  airbrake-ruby (2.5.0) lib/airbrake-ruby/filters/keys_filter.rb:134:in `filter_context_key'
  airbrake-ruby (2.5.0) lib/airbrake-ruby/filters/keys_filter.rb:61:in `block in call'
  airbrake-ruby (2.5.0) lib/airbrake-ruby/filters/keys_filter.rb:61:in `each'
  airbrake-ruby (2.5.0) lib/airbrake-ruby/filters/keys_filter.rb:61:in `call'
  airbrake-ruby (2.5.0) lib/airbrake-ruby/filter_chain.rb:47:in `block in refine'
  airbrake-ruby (2.5.0) lib/airbrake-ruby/filter_chain.rb:45:in `each'
  airbrake-ruby (2.5.0) lib/airbrake-ruby/filter_chain.rb:45:in `refine'
  airbrake-ruby (2.5.0) lib/airbrake-ruby/notifier.rb:126:in `send_notice'
  airbrake-ruby (2.5.0) lib/airbrake-ruby/notifier.rb:50:in `notify'
  airbrake (7.1.0) lib/airbrake/rack/middleware.rb:80:in `notify_airbrake'
  airbrake (7.1.0) lib/airbrake/rack/middleware.rb:54:in `rescue in call'
  airbrake (7.1.0) lib/airbrake/rack/middleware.rb:51:in `call'
  activerecord (4.2.9) lib/active_record/connection_adapters/abstract/connection_pool.rb:653:in `call'
  actionpack (4.2.9) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
  activesupport (4.2.9) lib/active_support/callbacks.rb:88:in `__run_callbacks__'
  activesupport (4.2.9) lib/active_support/callbacks.rb:778:in `_run_call_callbacks'
  activesupport (4.2.9) lib/active_support/callbacks.rb:81:in `run_callbacks'
  actionpack (4.2.9) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (4.2.9) lib/action_dispatch/middleware/reloader.rb:73:in `call'
  actionpack (4.2.9) lib/action_dispatch/middleware/remote_ip.rb:78:in `call'
  actionpack (4.2.9) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  actionpack (4.2.9) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.2.9) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.2.9) lib/rails/rack/logger.rb:20:in `block in call'
  activesupport (4.2.9) lib/active_support/tagged_logging.rb:68:in `block in tagged'
  activesupport (4.2.9) lib/active_support/tagged_logging.rb:26:in `tagged'
  activesupport (4.2.9) lib/active_support/tagged_logging.rb:68:in `tagged'
  railties (4.2.9) lib/rails/rack/logger.rb:20:in `call'
  actionpack (4.2.9) lib/action_dispatch/middleware/request_id.rb:21:in `call'
  rack (1.6.8) lib/rack/methodoverride.rb:22:in `call'
  rack (1.6.8) lib/rack/runtime.rb:18:in `call'
  rack (1.6.8) lib/rack/lock.rb:17:in `call'
  rack-livereload (0.3.16) lib/rack/livereload.rb:23:in `_call'
  rack-livereload (0.3.16) lib/rack/livereload.rb:14:in `call'
  actionpack (4.2.9) lib/action_dispatch/middleware/static.rb:120:in `call'
  rack (1.6.8) lib/rack/sendfile.rb:113:in `call'
  railties (4.2.9) lib/rails/engine.rb:518:in `call'
  railties (4.2.9) lib/rails/application.rb:165:in `call'
  rack (1.6.8) lib/rack/content_length.rb:15:in `call'
  thin (1.5.1) lib/thin/connection.rb:81:in `block in pre_process'
  thin (1.5.1) lib/thin/connection.rb:79:in `catch'
  thin (1.5.1) lib/thin/connection.rb:79:in `pre_process'
  thin (1.5.1) lib/thin/connection.rb:54:in `process'
  thin (1.5.1) lib/thin/connection.rb:39:in `receive_data'
  eventmachine (1.0.9.1) lib/eventmachine.rb:193:in `run_machine'
  eventmachine (1.0.9.1) lib/eventmachine.rb:193:in `run'
  thin (1.5.1) lib/thin/backends/base.rb:63:in `start'
  thin (1.5.1) lib/thin/server.rb:159:in `start'
  rack (1.6.8) lib/rack/handler/thin.rb:19:in `run'
  rack (1.6.8) lib/rack/server.rb:287:in `start'
  railties (4.2.9) lib/rails/commands/server.rb:80:in `start'
  railties (4.2.9) lib/rails/commands/commands_tasks.rb:80:in `block in server'
  railties (4.2.9) lib/rails/commands/commands_tasks.rb:75:in `tap'
  railties (4.2.9) lib/rails/commands/commands_tasks.rb:75:in `server'
  railties (4.2.9) lib/rails/commands/commands_tasks.rb:39:in `run_command!'
  railties (4.2.9) lib/rails/commands.rb:17:in `<top (required)>'
  bin/rails:4:in `require'
  bin/rails:4:in `<main>