NoMethodError: undefined method `match' for nil:NilClass

c:/github/web_server_ir/web_server.rb:115:in `host_parts'
c:/github/web_server_ir/web_server.rb:119:in `host_server'
c:/github/web_server_ir/web_server.rb:38:in `base_url'
c:/github/web_server_ir/xslt_web_server.rb:52:in `get_response'
c:/github/web_server_ir/web_server.rb:78:in `get_and_process_request'
c:/github/web_server_ir/tools.rb:21:in `measure_duration'
c:/github/web_server_ir/web_server.rb:57:in `get_and_process_request'
c:/github/web_server_ir/web_server.rb:47:in `start'
register.rb:24