FIX: Define s3_helper in EnsureS3UploadsExistence job

FIX: Define s3_helper in EnsureS3UploadsExistence job

Followup to 16c65a94

diff --git a/app/jobs/scheduled/ensure_s3_uploads_existence.rb b/app/jobs/scheduled/ensure_s3_uploads_existence.rb
index 6e2d671..99a99ed 100644
--- a/app/jobs/scheduled/ensure_s3_uploads_existence.rb
+++ b/app/jobs/scheduled/ensure_s3_uploads_existence.rb
@@ -13,6 +13,10 @@ module Jobs
       end
     end
 
+    def s3_helper
+      Discourse.store.s3_helper
+    end
+
     def prepare_for_all_sites
       inventory = S3Inventory.new(s3_helper, :upload)
       @db_inventories = inventory.prepare_for_all_sites

GitHub sha: 4ef389bc