Full backtrace

!! Unexpected error while processing request: undefined method `call' for nil:NilClass
undefined method `call' for nil:NilClass
	/home/max/git/rack/lib/rack/builder.rb:60:in `call'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/connection.rb:76:in `pre_process'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/connection.rb:74:in `catch'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/connection.rb:74:in `pre_process'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/connection.rb:57:in `process'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/connection.rb:42:in `receive_data'
	/usr/lib/ruby/gems/1.8/gems/eventmachine-0.12.10/lib/eventmachine.rb:256:in `run_machine'
	/usr/lib/ruby/gems/1.8/gems/eventmachine-0.12.10/lib/eventmachine.rb:256:in `run'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/backends/base.rb:57:in `start'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/server.rb:156:in `start'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/controllers/controller.rb:80:in `start'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/runner.rb:174:in `send'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/runner.rb:174:in `run_command'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/lib/thin/runner.rb:140:in `run!'
	/usr/lib/ruby/gems/1.8/gems/thin-1.2.4/bin/thin:6
	/usr/bin/thin:19:in `load'
	/usr/bin/thin:19

gistfile1.txt

require 'main'

run Rack::Builder.new do
	use Rack::CommonLogger
 	use Rack::ShowExceptions
 	map '/monkey' do
	  use Rack::Lint
		lambda { |env| [200, {'Content-Type' => 'text/plain'}, 'OK'] }
	 end

 	map '/tree' do
		run Sinatra::Application
	end
end