fix social share helper

app/helpers/learning_objects_helper.rb

@@ -50,14 +50,14 @@ module LearningObjectsHelper
 
   def social_share(learning_object)
     set_meta_tags og: {
-        title: @learning_object.name,
-        type: 'website',
-        description: @learning_object.description,
-        image: @learning_object.thumbnail
+      title: learning_object.name,
+      type: 'website',
+      description: learning_object.description,
+      image: learning_object.default_thumbnail
     }
 
     set_meta_tags fb: {
-        app_id: '745857965514514'
+      app_id: '745857965514514'
     }
   end
 end