title: "incompatible character encodings: UTF-8 and ASCII-8BIT" on some redmine pages
body: <p>After migration of redmine 1.3.1.stable to 2.5.1.stable. All work fine exept on some of page:</p>
  
  <p><strong>Administration / Settings</strong> :</p>
  
  <pre><code>Started GET "/settings" for 80.13.99.120 at 2014-04-25 09:23:25 +0200
  Processing by SettingsController#index as HTML
    Current user: bux (id=1)
    Rendered settings/_general.html.erb (6.8ms)
    Rendered settings/_display.html.erb (4.3ms)
    Rendered common/_tabs.html.erb (14.8ms)
    Rendered settings/edit.html.erb within layouts/admin (15.3ms)
  Completed 500 Internal Server Error in 20.4ms
  
  ActionView::Template::Error (incompatible character encodings: UTF-8 and ASCII-8BIT):
      3: &lt;div class="box tabular settings"&gt;
      4: &lt;p&gt;&lt;%= setting_select :ui_theme, Redmine::Themes.themes.collect {|t| [t.name, t.id]}, :blank =&gt; :label_default, :label =&gt; :label_theme %&gt;&lt;/p&gt;
      5: 
      6: &lt;p&gt;&lt;%= setting_select :default_language, lang_options_for_select(false) %&gt;&lt;/p&gt;
      7: 
      8: &lt;p&gt;&lt;%= setting_check_box :force_default_language_for_anonymous %&gt;&lt;/p&gt;
      9: 
    app/helpers/settings_helper.rb:40:in `setting_select'
    app/views/settings/_display.html.erb:6:in `block in _app_views_settings__display_html_erb__360450665_108765910'
    app/views/settings/_display.html.erb:1:in `_app_views_settings__display_html_erb__360450665_108765910'
    app/views/common/_tabs.html.erb:22:in `block in _app_views_common__tabs_html_erb__1065101303_107873960'
    app/views/common/_tabs.html.erb:21:in `each'
    app/views/common/_tabs.html.erb:21:in `_app_views_common__tabs_html_erb__1065101303_107873960'
    app/helpers/application_helper.rb:318:in `render_tabs'
    app/views/settings/edit.html.erb:3:in `_app_views_settings_edit_html_erb___826014255_106971690'
    app/controllers/settings_controller.rb:28:in `index'
  </code></pre>
  
  <p>Same error on the user edit page, etc ... </p>