process_parameter_filter throws an exception on array parameters

Same here, but with a slightly different error message:

irb(main):007:0> app.get '/?foo[]=bar&foo[]=pub'
NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.each
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/http/filter_parameters.rb:78:in `process_parameter_filter'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/http/filter_parameters.rb:84:in `process_parameter_filter'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/http/filter_parameters.rb:84:in `map'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/http/filter_parameters.rb:84:in `process_parameter_filter'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/http/filter_parameters.rb:78:in `each'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/http/filter_parameters.rb:78:in `process_parameter_filter'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/http/filter_parameters.rb:30:in `filtered_parameters'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_controller/metal/instrumentation.rb:20:in `process_action'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_controller/metal/rescue.rb:8:in `process_action'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/abstract_controller/base.rb:115:in `process'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_controller/metal.rb:64:in `dispatch'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_controller/metal/rack_delegation.rb:19:in `dispatch'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_controller/metal.rb:89:in `call'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/routing/route_set.rb:27:in `call'
    from /Users/marco/.bundle/ruby/1.8/gems/rack-mount-0.4.7/lib/rack/mount/recognition/route_set.rb:70:in `call'
    from /Users/marco/.bundle/ruby/1.8/gems/rack-mount-0.4.7/lib/rack/mount/recognition/code_generation.rb:97:in `recognize'

... 18 levels...

    from /opt/local/lib/ruby/gems/1.8/gems/activesupport-3.0.0.beta/lib/active_support/callbacks.rb:88:in `run_callbacks'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/middleware/callbacks.rb:44:in `call'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/middleware/show_exceptions.rb:62:in `call'
    from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.0.beta/lib/rails/rack/logger.rb:13:in `call'
    from /opt/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/runtime.rb:17:in `call'
    from /opt/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/lock.rb:11:in `call'
    from /opt/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/lock.rb:11:in `synchronize'
    from /opt/local/lib/ruby/gems/1.8/gems/rack-1.1.0/lib/rack/lock.rb:11:in `call'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/middleware/static.rb:30:in `call'
    from /opt/local/lib/ruby/gems/1.8/gems/railties-3.0.0.beta/lib/rails/application.rb:95:in `call'
    from /opt/local/lib/ruby/gems/1.8/gems/rack-test-0.5.3/lib/rack/mock_session.rb:30:in `request'
    from /opt/local/lib/ruby/gems/1.8/gems/rack-test-0.5.3/lib/rack/test.rb:207:in `process_request'
    from /opt/local/lib/ruby/gems/1.8/gems/rack-test-0.5.3/lib/rack/test.rb:105:in `request'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/testing/integration.rb:272:in `process'
    from /opt/local/lib/ruby/gems/1.8/gems/actionpack-3.0.0.beta/lib/action_dispatch/testing/integration.rb:30:in `get'

Fixed!

Automatic cleanup of spam.