Fix RecordNotFound bug for application associated workshops that have been deleted

dashboard/app/models/pd/application/workshop_autoenrolled_application.rb

@@ -56,7 +56,7 @@ def destroy_autoenrollment
     end
 
     def workshop
-      Pd::Workshop.find(pd_workshop_id) if pd_workshop_id
+      Pd::Workshop.find_by(id: pd_workshop_id) if pd_workshop_id
     end
 
     # override

dashboard/test/factories/pd_factories.rb

@@ -738,6 +738,8 @@
     end
   end
 
+  factory :pd_workshop_autoenrolled_application, parent: :pd_teacher1819_application
+
   # default to do_you_approve: other
   factory :pd_principal_approval1819_application_hash, parent: :pd_principal_approval1819_application_hash_common do
     approved_other

dashboard/test/models/pd/application/workshop_autoenrolled_application_test.rb

@@ -0,0 +1,21 @@
+require 'test_helper'
+require 'cdo/shared_constants/pd/teacher1819_application_constants'
+
+module Pd::Application
+  class WorkshopAutoenrolledApplicationTest < ActiveSupport::TestCase
+    self.use_transactional_test_case = true
+    setup_all do
+      @workshop = create :pd_workshop
+      @application = create :pd_workshop_autoenrolled_application, pd_workshop_id: @workshop.id
+    end
+
+    test 'application.workshop returns the workshop associated with the assigned id' do
+      assert_equal @workshop, @application.workshop
+    end
+
+    test 'application.workshop returns nil if the assigned workshop has been deleted' do
+      @workshop.destroy!
+      assert_nil @application.workshop
+    end
+  end
+end