Problem application Rails 2 using bundler

I am using Rails 2.3.11 end the error is:

NoMethodError in Configurations#index

Showing rails/ruby/1.8/gems/actionpack-2.3.11/lib/action_controller/templates/rescues/diagnostics.erb where line #7 raised:

private method `gsub' called for nil:NilClass

Extracted source (around line #7):

4: in <%=h request.parameters['controller'].humanize %>Controller<% if request.parameters['action'] %>#<%=h request.parameters['action'] %><% end %>
5: <% end %&g开发者_如何学运维t;
6: </h1>
7: <pre><%=h @exception.clean_message %></pre>
8: 
9: <%= render :file => @rescues_path["rescues/_trace.erb"] %>
10: 

My feeling is that @exception is null, since no exceptions were raised on page.

Try something like:

<% if !@exception.nil? %>
   <%=h @exception.clean_message %>
<% end %>