Fix observer workers so that they don't raise error if item is already deleted

app/jobs/abf_worker/base_observer.rb

@@ -24,7 +24,7 @@ module AbfWorker
     protected
 
     def subject
-      @subject ||= @subject_class.find(options['id'])
+      @subject ||= @subject_class.find(options['id']) rescue nil
     end
 
     def update_results

app/jobs/abf_worker/iso_worker_observer.rb

@@ -4,6 +4,7 @@ module AbfWorker
 
     def real_perform
       @subject_class = ProductBuildList
+      return if !subject
       subject.with_lock do
         case status
         when COMPLETED

app/jobs/abf_worker/publish_observer.rb

@@ -4,6 +4,7 @@ module AbfWorker
 
     def real_perform
       @subject_class = BuildList
+      return if !subject
       return if status == STARTED # do nothing when publication started
       extra = options['extra']
       repository_status = RepositoryStatus.where(id: extra['repository_status_id']).first

app/jobs/abf_worker/rpm_worker_observer.rb

@@ -11,10 +11,11 @@ module AbfWorker
 
     def real_perform
       @subject_class = BuildList
+      return if !subject
       unless subject.valid? && restart_task
         if options['feedback_from_user']
           user = User.find options['feedback_from_user']
-          raise ActiveRecord::Rollback if !user.system? && subject.builder != user
+          return if !user.system? && subject.builder != user
         end
 
         fill_container_data if status != STARTED