Error 500 when consulting an issue

[azmeuk]

Hi,
I have an error 500 when consulting an issue, and I don't get it when I disable redmine_category_tree

This is the information displayed in the admin panel:

Environment:
  Redmine version                          2.3.1.stable.11838
  Ruby version                             1.9.3 (x86_64-linux)
  Rails version                            3.2.13
  Environment                              production
  Database adapter                         Mysql2
Redmine plugins:
  redmine_category_tree                    0.0.1
  redmine_ckeditor                         1.0.4
  redmine_ldap_sync                        2.0.0.devel
  redmine_logs                             0.0.5
  redmine_tags                             2.0.1-dev

This is my log.

Started GET "/issues/1" for 172.17.4.10 at 2013-05-14 16:49:38 +0200
Processing by IssuesController#show as HTML
  Parameters: {"id"=>"1"}
  Current user: admin (id=1)
  Rendered issues/_action_menu.html.erb (4.3ms)
  Rendered plugins/redmine_category_tree/app/views/issues/show.html.erb within layouts/base (13.3ms)
Completed 500 Internal Server Error in 74ms

ActionView::Template::Error (undefined method `root?' for nil:NilClass):
    40:     rows.left l(:field_assigned_to), avatar(@issue.assigned_to, :size => "14").to_s.html_safe + (@issue.assigned_to ? link_to_user(@issue.assigned_to) : "-"), :class => 'assigned-to'
    41:   end
    42:   unless @issue.disabled_core_fields.include?('category_id')
    43:     rows.left l(:field_category), render_issue_category_with_tree(@issue.category), :class => 'category'
    44:   end
    45:   unless @issue.disabled_core_fields.include?('fixed_version_id')
    46:     rows.left l(:field_fixed_version), (@issue.fixed_version ? link_to_version(@issue.fixed_version) : "-"), :class => 'fixed-version'
  app/helpers/issues_helper.rb:144:in `issue_fields_rows'
  app/controllers/issues_controller.rb:119:in `block (2 levels) in show'
  app/controllers/issues_controller.rb:116:in `show'

[ghost]

I have merged a fix from KappaNossi which I believe will fix this error. Please upgrade your installation and let me know if it's fixed.

[ghost]

Closing due to lack of response.