Redmine

i got Error 500 in one of issues

production.log:

Started GET "/issues/7815" for 91.205.47.195 at 2015-11-03 18:08:47 +0300
Processing by IssuesController#show as HTML
  Parameters: {"id"=>"7815"}
  Current user: s.bondarev (id=141)
  Rendered issues/_action_menu.html.erb (3.7ms)
  Rendered attachments/_links.html.erb (4.0ms)
  Rendered issue_relations/_form.html.erb (1.8ms)
  Rendered issues/_relations.html.erb (2.6ms)
  Rendered issues/_history.html.erb (53.1ms)
  Rendered issues/show.html.erb within layouts/base (92.8ms)
Completed 500 Internal Server Error in 157ms (ActiveRecord: 12.4ms)

ActionView::Template::Error (undefined method `project' for nil:NilClass):
     9:
    10:     <% if journal.details.any? %>
    11:     <ul class="details">
    12:       <% details_to_strings(journal.visible_details).each do |string| %>
    13:        <li><%= string %></li>
    14:       <% end %>
    15:     </ul>
  app/helpers/issues_helper.rb:345:in `block in details_to_strings'
  app/helpers/issues_helper.rb:331:in `each'
  app/helpers/issues_helper.rb:331:in `details_to_strings'
  app/views/issues/_history.html.erb:12:in `block in _app_views_issues__history_html_erb__756860947688524154_82188920'
  app/views/issues/_history.html.erb:2:in `each'
  app/views/issues/_history.html.erb:2:in `_app_views_issues__history_html_erb__756860947688524154_82188920'
  app/views/issues/show.html.erb:124:in `_app_views_issues_show_html_erb___3370798931249239145_33577620'
  app/controllers/issues_controller.rb:118:in `block (2 levels) in show'
  app/controllers/issues_controller.rb:115:in `show'
  lib/redmine/sudo_mode.rb:63:in `sudo_mode'