FIX: do not stop `fix_missing_s3` task if saving an upload failed (PR #13658)

This commit logs an error and moves to next upload when saving a single upload record fails when running uploads:fix_missing_s3 task.

GitHub

        upload.assign_attributes(etag: fixed_upload.etag, url: fixed_upload.url, verification_status: Upload.verification_statuses[:unchecked])
        saved = upload.save(validate: false)

(then invert the if block below using the saved var)

Made the change.