fix learning object show

app/helpers/learning_objects_helper.rb

 module LearningObjectsHelper
 
   def display_object_type(learning_object)
-    case learning_object.default_attachment.mime_type
+    case learning_object.default_attachment.try(:mime_type)
       when /audio\/*/i then
         audio_tag(learning_object.cache_link, controls: true)
       when /video\/mp4/i then
@@ -86,7 +86,7 @@ module LearningObjectsHelper
 
   def highlighted_btn(url, _label = nil, _class = nil)
     link_to url, class: 'download btn btn-success', target: "_blank" do
-      content_tag(:i, _label, class: "fa #{_class}").html_safe
+      "<i class='fa #{_class}'></i> #{_label}".html_safe
     end
   end
 end