fix

app/models/education/program.rb

@@ -151,11 +151,6 @@ class Education::Program < ApplicationRecord
   end
 
   def references
-    []
-  end
-
-  def references
-    siblings +
     descendants
   end
 

app/views/admin/communication/blocks/templates/programs/_preview.html.erb

@@ -21,7 +21,7 @@ end
           next if program.nil?
         %>
           <li>
-            <%= link_to program, [:admin, program] %>  
+            <%= link_to program, [:admin, program] %>
           </li>
         <% end %>
       </ol>