Error on adding a Sprint

[TsPG128]

I'm getting a internal server error on adding a sprint (the sprint is created)

The error log:

Started POST "/scrum_sprints_planning/add_version?project_id=test-project" for 109.84.191.68 at Wed May 01 11:06:45 +0200 2013
Processing by ScrumSprintsPlanningController#add_version as HTML
  Parameters: {"commit"=>"Anlegen", "project_id"=>"test-project", "version_id"=>"", "authenticity_token"=>"(hidden)", "utf8"=>"", "version"=>{"name"=>"Sprint 2", "custom_field_values"=>{"2"=>"2013-05-16"}, "description"=>"", "release_id"=>"1", "effective_date"=>"2013-05-31", "status"=>"open", "sharing"=>"none"}}
  Current user: tspigel (id=40)
Completed 500 Internal Server Error in 85ms

NoMethodError (undefined method `project' for nil:NilClass):
  plugins/redmine_scrummer/app/controllers/scrum_sprints_planning_controller.rb:127:in `create_sprint'
  plugins/redmine_scrummer/app/controllers/scrum_sprints_planning_controller.rb:68:in `add_version'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_controller/metal/implicit_render.rb:4:in `send_action'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_controller/metal/implicit_render.rb:4:in `send_action'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/abstract_controller/base.rb:167:in `process_action'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_controller/metal/rendering.rb:10:in `process_action'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/abstract_controller/callbacks.rb:18:in `process_action'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:491:in `_run__1824751542__process_action__265282519__callbacks'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:405:in `send'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:405:in `__run_callback'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:81:in `send'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:81:in `run_callbacks'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/abstract_controller/callbacks.rb:17:in `process_action'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_controller/metal/rescue.rb:29:in `process_action'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/notifications.rb:123:in `instrument'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/notifications.rb:123:in `instrument'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_controller/metal/instrumentation.rb:29:in `process_action'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_controller/metal/params_wrapper.rb:207:in `process_action'
  vendor/bundle/ruby/1.8/gems/activerecord-3.2.11/lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/abstract_controller/base.rb:121:in `process'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/abstract_controller/rendering.rb:45:in `process'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_controller/metal.rb:203:in `dispatch'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_controller/metal.rb:246:in `action'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/routing/route_set.rb:73:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/routing/route_set.rb:36:in `call'
  vendor/bundle/ruby/1.8/gems/journey-1.0.4/lib/journey/router.rb:68:in `call'
  vendor/bundle/ruby/1.8/gems/journey-1.0.4/lib/journey/router.rb:56:in `each'
  vendor/bundle/ruby/1.8/gems/journey-1.0.4/lib/journey/router.rb:56:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/routing/route_set.rb:601:in `call'
  vendor/bundle/ruby/1.8/gems/rack-openid-1.3.1/lib/rack/openid.rb:98:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
  vendor/bundle/ruby/1.8/gems/rack-1.4.5/lib/rack/etag.rb:23:in `call'
  vendor/bundle/ruby/1.8/gems/rack-1.4.5/lib/rack/conditionalget.rb:35:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/head.rb:14:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/params_parser.rb:21:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/flash.rb:242:in `call'
  vendor/bundle/ruby/1.8/gems/rack-1.4.5/lib/rack/session/abstract/id.rb:210:in `context'
  vendor/bundle/ruby/1.8/gems/rack-1.4.5/lib/rack/session/abstract/id.rb:205:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/cookies.rb:341:in `call'
  vendor/bundle/ruby/1.8/gems/activerecord-3.2.11/lib/active_record/query_cache.rb:64:in `call'
  vendor/bundle/ruby/1.8/gems/activerecord-3.2.11/lib/active_record/connection_adapters/abstract/connection_pool.rb:479:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/callbacks.rb:28:in `call'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:405:in `_run__397314981__call__4__callbacks'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:405:in `send'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:405:in `__run_callback'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:81:in `send'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/callbacks.rb:81:in `run_callbacks'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
  vendor/bundle/ruby/1.8/gems/railties-3.2.11/lib/rails/rack/logger.rb:32:in `call_app'
  vendor/bundle/ruby/1.8/gems/railties-3.2.11/lib/rails/rack/logger.rb:16:in `call'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/tagged_logging.rb:22:in `tagged'
  vendor/bundle/ruby/1.8/gems/railties-3.2.11/lib/rails/rack/logger.rb:16:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/request_id.rb:22:in `call'
  vendor/bundle/ruby/1.8/gems/rack-1.4.5/lib/rack/methodoverride.rb:21:in `call'
  vendor/bundle/ruby/1.8/gems/rack-1.4.5/lib/rack/runtime.rb:17:in `call'
  vendor/bundle/ruby/1.8/gems/activesupport-3.2.11/lib/active_support/cache/strategy/local_cache.rb:72:in `call'
  vendor/bundle/ruby/1.8/gems/rack-1.4.5/lib/rack/lock.rb:15:in `call'
  vendor/bundle/ruby/1.8/gems/actionpack-3.2.11/lib/action_dispatch/middleware/static.rb:62:in `call'
  vendor/bundle/ruby/1.8/gems/rack-cache-1.2/lib/rack/cache/context.rb:136:in `forward'
  vendor/bundle/ruby/1.8/gems/rack-cache-1.2/lib/rack/cache/context.rb:143:in `pass'
  vendor/bundle/ruby/1.8/gems/rack-cache-1.2/lib/rack/cache/context.rb:155:in `invalidate'
  vendor/bundle/ruby/1.8/gems/rack-cache-1.2/lib/rack/cache/context.rb:71:in `call!'
  vendor/bundle/ruby/1.8/gems/rack-cache-1.2/lib/rack/cache/context.rb:51:in `call'
  vendor/bundle/ruby/1.8/gems/railties-3.2.11/lib/rails/engine.rb:479:in `call'
  vendor/bundle/ruby/1.8/gems/railties-3.2.11/lib/rails/application.rb:223:in `call'
  vendor/bundle/ruby/1.8/gems/railties-3.2.11/lib/rails/railtie/configurable.rb:30:in `send'
  vendor/bundle/ruby/1.8/gems/railties-3.2.11/lib/rails/railtie/configurable.rb:30:in `method_missing'
  /usr/lib/ruby/1.8/phusion_passenger/rack/request_handler.rb:92:in `process_request'
  /usr/lib/ruby/1.8/phusion_passenger/abstract_request_handler.rb:207:in `main_loop'
  /usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:118:in `run'
  /usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:65:in `spawn_application'
  /usr/lib/ruby/1.8/phusion_passenger/utils.rb:184:in `safe_fork'
  /usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:58:in `spawn_application'
  /usr/lib/ruby/1.8/phusion_passenger/rack/application_spawner.rb:41:in `spawn_application'
  /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:159:in `spawn_application'
  /usr/lib/ruby/1.8/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application'
  /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `__send__'
  /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:352:in `main_loop'
  /usr/lib/ruby/1.8/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
  /usr/lib/phusion_passenger/passenger-spawn-server:61