only showing enabled story trackers in story form

ref #3786

app/helpers/rb_common_helper.rb

@@ -116,4 +116,13 @@ module RbCommonHelper
     args.push(:plugin => 'redmine_backlogs')
     javascript_include_tag *args
   end
+
+  def available_story_trackers
+    trackers = Tracker.find(:all, :conditions => {:id => Setting.plugin_redmine_backlogs[:story_trackers]},
+                                  :order => 'position')
+
+    trackers &= @project.trackers if @project
+
+    trackers
+  end
 end

app/views/rb_stories/_helpers.html.erb

@@ -8,7 +8,7 @@
 </select>
 
 <select class="tracker_id helper" id="tracker_id_options">
-  <% Tracker.find_all_by_id(Setting.plugin_redmine_backlogs[:story_trackers]).each do |tracker| %>
+  <% available_story_trackers.each do |tracker| %>
     <option value="<%= tracker.id %>">
       <%= tracker.name %>
     </option>