redmine error

gistfile1.txt

ActionView::Template::Error (no implicit conversion of Symbol into Integer):
    9: <%= favicon %>
    10: <%= stylesheet_link_tag 'jquery/jquery-ui-1.9.2', 'application', :media => 'all' %>
    11: <%= stylesheet_link_tag 'rtl', :media => 'all' if l(:direction) == 'rtl' %>
    12: <%= javascript_heads %>
    13: <%= heads_for_theme %>
    14: <%= call_hook :view_layouts_base_html_head %>
    15: <!-- page specific tags -->
  app/models/user_preference.rb:41:in `[]'
  app/models/user_preference.rb:41:in `[]'
  app/models/user_preference.rb:61:in `warn_on_leaving_unsaved'
  app/helpers/application_helper.rb:1289:in `javascript_heads'
  app/views/layouts/base.html.erb:12:in `_app_views_layouts_base_html_erb___1143727979315042903_17237980460'