Fix duplicated 'back_url' IDs

Various hidden input fields are used to hold a URL to send the user back
to the correct page after submitting a form, however, they all use the
same ID which isn't allowed in HTML. Passing in 'id' as nil stops the
'hidden_field_tag' from adding an ID attribute to the tag.

app/helpers/application_helper.rb

@@ -851,7 +851,7 @@ module ApplicationHelper
   def back_url_hidden_field_tag
     back_url = params[:back_url] || request.env['HTTP_REFERER']
     back_url = CGI.unescape(back_url.to_s)
-    hidden_field_tag('back_url', CGI.escape(back_url)) unless back_url.blank?
+    hidden_field_tag('back_url', CGI.escape(back_url), :id => nil) unless back_url.blank?
   end
 
   def check_all_links(form_name)

app/views/account/_login.rhtml

@@ -1,6 +1,6 @@
 <div id="nav-login-content">
   <% form_tag({:controller => "account", :action=> "login"}) do %>
-    <%= hidden_field_tag('back_url', CGI.escape(request.url))  %>
+    <%= hidden_field_tag 'back_url', CGI.escape(request.url), :id => nil  %>
     <table>
       <tr>
         <td><label for="username-pulldown"><%= l(:field_login) %></label></td>

app/views/issues/_list.rhtml

@@ -1,5 +1,5 @@
 <% form_tag({}) do -%>
-<%= hidden_field_tag 'back_url', url_for(params) %>
+<%= hidden_field_tag 'back_url', url_for(params), :id => nil %>
 <div class="autoscroll">
 <table class="list issues">
     <thead><tr>