Redmine

When I try to open 'Repository' tab in one of the our projects I get 500 error:

Internal error

An error occurred on the page you were trying to access.
If you continue to experience problems please contact your redMine administrator for assistance.

And everything is ok with all other projects in this redmine installation.

redmine: 1.0.1
ruby: 4.5
rails: 2.3.5

Part of the log file:

Processing RepositoriesController#show (for 10.68.60.76 at 2010-10-14 10:25:36) [GET]
  Parameters: {"action"=>"show", "id"=>"a4repo", "controller"=>"repositories"}

NoMethodError (undefined method `left' for nil:NilClass):
  /usr/lib/ruby/1.8/active_record/associations/association_proxy.rb:217:in `send'
  /usr/lib/ruby/1.8/active_record/associations/association_proxy.rb:217:in `method_missing'
  app/models/changeset.rb:171:in `find_referenced_issues_by_id'
  app/models/changeset.rb:170:in `select'
  app/models/changeset.rb:170:in `find_referenced_issues_by_id'
  app/models/changeset.rb:96:in `scan_comment_for_issue_ids'
  app/models/changeset.rb:77:in `after_create'
  /usr/lib/ruby/1.8/active_record/callbacks.rb:347:in `send'
  /usr/lib/ruby/1.8/active_record/callbacks.rb:347:in `callback'
  /usr/lib/ruby/1.8/active_record/callbacks.rb:267:in `create'
  /usr/lib/ruby/1.8/active_record/base.rb:2874:in `create_or_update_without_callbacks'
  /usr/lib/ruby/1.8/active_record/callbacks.rb:250:in `create_or_update'
  /usr/lib/ruby/1.8/active_record/base.rb:2538:in `save_without_validation'
  /usr/lib/ruby/1.8/active_record/validations.rb:1078:in `save_without_dirty'
  /usr/lib/ruby/1.8/active_record/dirty.rb:79:in `save_without_transactions'
  /usr/lib/ruby/1.8/active_record/transactions.rb:229:in `send'
  /usr/lib/ruby/1.8/active_record/transactions.rb:229:in `with_transaction_returning_status'
  /usr/lib/ruby/1.8/active_record/connection_adapters/abstract/database_statements.rb:136:in `transaction'
  /usr/lib/ruby/1.8/active_record/transactions.rb:182:in `transaction'
  /usr/lib/ruby/1.8/active_record/transactions.rb:228:in `with_transaction_returning_status'
  /usr/lib/ruby/1.8/active_record/transactions.rb:196:in `save'
  /usr/lib/ruby/1.8/active_record/transactions.rb:208:in `rollback_active_record_state!'
  /usr/lib/ruby/1.8/active_record/transactions.rb:196:in `save'
  /usr/lib/ruby/1.8/active_record/base.rb:723:in `create'
  app/models/repository/subversion.rb:59:in `fetch_changesets'
  /usr/lib/ruby/1.8/active_record/connection_adapters/abstract/database_statements.rb:136:in `transaction'
  /usr/lib/ruby/1.8/active_record/transactions.rb:182:in `transaction'
  /usr/lib/ruby/1.8/active_record/transactions.rb:188:in `transaction'
  app/models/repository/subversion.rb:58:in `fetch_changesets'
  app/models/repository/subversion.rb:57:in `reverse_each'
  app/models/repository/subversion.rb:57:in `fetch_changesets'
  /usr/lib/ruby/1.8/active_record/associations/association_proxy.rb:217:in `send'
  /usr/lib/ruby/1.8/active_record/associations/association_proxy.rb:217:in `method_missing'
  app/controllers/repositories_controller.rb:77:in `show'
  /usr/lib/ruby/1.8/action_controller/base.rb:1331:in `send'
  /usr/lib/ruby/1.8/action_controller/base.rb:1331:in `perform_action_without_filters'
  /usr/lib/ruby/1.8/action_controller/filters.rb:617:in `call_filters'
  /usr/lib/ruby/1.8/action_controller/filters.rb:610:in `perform_action_without_benchmark'
  /usr/lib/ruby/1.8/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
  /usr/lib/ruby/1.8/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
  /usr/lib/ruby/1.8/action_controller/rescue.rb:160:in `perform_action_without_flash'
  /usr/lib/ruby/1.8/action_controller/flash.rb:146:in `perform_action'
  /usr/lib/ruby/1.8/action_controller/base.rb:532:in `send'
  /usr/lib/ruby/1.8/action_controller/base.rb:532:in `process_without_filters'
  /usr/lib/ruby/1.8/action_controller/filters.rb:606:in `process'
  /usr/lib/ruby/1.8/action_controller/base.rb:391:in `process'
  /usr/lib/ruby/1.8/action_controller/base.rb:386:in `call'
  /usr/lib/ruby/1.8/action_controller/routing/route_set.rb:437:in `call'
  /usr/lib/ruby/1.8/action_controller/dispatcher.rb:87:in `dispatch'
  /usr/lib/ruby/1.8/action_controller/dispatcher.rb:121:in `_call'
  /usr/lib/ruby/1.8/action_controller/dispatcher.rb:130
  /usr/lib/ruby/1.8/active_record/query_cache.rb:29:in `call'
  /usr/lib/ruby/1.8/active_record/query_cache.rb:29:in `call'
  /usr/lib/ruby/1.8/active_record/connection_adapters/abstract/query_cache.rb:34:in `cache'
  /usr/lib/ruby/1.8/active_record/query_cache.rb:9:in `cache'
  /usr/lib/ruby/1.8/active_record/query_cache.rb:28:in `call'
  /usr/lib/ruby/1.8/active_record/connection_adapters/abstract/connection_pool.rb:361:in `call'
  /usr/lib/ruby/1.8/action_controller/string_coercion.rb:25:in `call'
  /usr/lib/ruby/1.8/rack/head.rb:9:in `call'
  /usr/lib/ruby/1.8/rack/methodoverride.rb:24:in `call'
  /usr/lib/ruby/1.8/action_controller/params_parser.rb:15:in `call'
  /usr/lib/ruby/1.8/action_controller/session/cookie_store.rb:93:in `call'
  /usr/lib/ruby/1.8/action_controller/failsafe.rb:26:in `call'
  /usr/lib/ruby/1.8/rack/lock.rb:11:in `call'
  /usr/lib/ruby/1.8/rack/lock.rb:11:in `synchronize'
  /usr/lib/ruby/1.8/rack/lock.rb:11:in `call'
  /usr/lib/ruby/1.8/action_controller/dispatcher.rb:106:in `call'
  /usr/lib/ruby/1.8/rack/content_length.rb:13:in `call'
  /usr/lib/ruby/1.8/rack/handler/fastcgi.rb:57:in `serve'
  public/dispatch.fcgi:24

Rendering /usr/share/redmine/public/500.html (500 Internal Server Error)