Redmine

Hello Everyone,

i migrated our trac (1.0) to redmine (2.1).
I completely went fine, and now every user etc is in our redmine installation.
But when i want to view a Ticket in the imported Project, i get a error 500.

In the log there is only this:

@

ActionView::Template::Error (undefined method `-' for nil:NilClass):
    4:     &lt;div id="note-<%= journal.indice >">
    5:     &lt;h4&gt;<= link_to "##{journal.indice}", {:anchor => "note-#{journal.indice}"}, :class => "journal-link" >
    6:     <= avatar(journal.user, :size => "24") >
    7:     <= authoring journal.created_on, journal.user, :label => :label_updated_time_by >&lt;/h4&gt;
    8:
    9:     < if journal.details.any? %>
    10:     &lt;ul class="details"&gt;
  app/helpers/application_helper.rb:358:in `time_tag'
  app/helpers/application_helper.rb:354:in `authoring'
  app/views/issues/_history.html.erb:7:in `_app_views_issues__history_html_erb__844258531_69992257774020'
  app/views/issues/_history.html.erb:2:in `each'
  app/views/issues/_history.html.erb:2:in `_app_views_issues__history_html_erb__844258531_69992257774020'
  app/views/issues/show.html.erb:122:in `_app_views_issues_show_html_erb__1870642514_69992257579400'
  app/controllers/issues_controller.rb:117:in `show'
  app/controllers/issues_controller.rb:114:in `show'
@

has anyone an idea?