Fixes #3787 - UploadCacheCleanupJob does not execute.

app/jobs/upload_cache_cleanup_job.rb

@@ -3,6 +3,7 @@
 class UploadCacheCleanupJob < ApplicationJob
   def perform
     taskbar_form_ids = Taskbar.with_form_id.filter_map(&:persisted_form_id)
+    return if store_object_id.blank?
 
     Store.where(store_object_id: store_object_id).where('created_at < ?', 1.month.ago).where.not(o_id: taskbar_form_ids).find_each do |store|
       Store.remove_item(store.id)
@@ -12,6 +13,6 @@ class UploadCacheCleanupJob < ApplicationJob
   private
 
   def store_object_id
-    Store::Object.lookup(name: 'UploadCache').id
+    Store::Object.lookup(name: 'UploadCache')&.id
   end
 end

db/migrate/20211005110047_issue3787_fix_job.rb

@@ -0,0 +1,11 @@
+# Copyright (C) 2012-2021 Zammad Foundation, http://zammad-foundation.org/
+
+class Issue3787FixJob < ActiveRecord::Migration[6.0]
+  def change
+
+    # return if it's a new setup
+    return if !Setting.exists?(name: 'system_init_done')
+
+    Scheduler.find_by(name: 'Delete old upload cache entries.').update(error_message: nil, status: nil, active: true)
+  end
+end

spec/jobs/upload_cache_cleanup_job_spec.rb

@@ -3,6 +3,7 @@
 require 'rails_helper'
 
 RSpec.describe UploadCacheCleanupJob, type: :job do
+  context 'when upload cache exists' do
     let(:upload_cache) { UploadCache.new(1337) }
 
     before do
@@ -44,4 +45,11 @@ RSpec.describe UploadCacheCleanupJob, type: :job do
     it 'cleanup the store items which are expired with job' do
       expect { described_class.perform_now }.to change(Store, :count).by(-3)
     end
+  end
+
+  context 'when upload cache does not exist' do
+    it 'does not crash' do
+      expect { described_class.perform_now }.not_to raise_error
+    end
+  end
 end