NoMethodError: undefined method `schedule_background_upload' for nil:NilClass

https://sentry.gitlab.net/gitlab/gitlabcom/issues/713867/

NoMethodError: undefined method `schedule_background_upload' for nil:NilClass
  object_storage.rb:109:in `block (2 levels) in background_upload'
    mount_points.each { |mount| send(mount).schedule_background_upload } # rubocop:disable GitlabSecurity/PublicSend
  object_storage.rb:109:in `each'
    mount_points.each { |mount| send(mount).schedule_background_upload } # rubocop:disable GitlabSecurity/PublicSend
  object_storage.rb:109:in `block in background_upload'
    mount_points.each { |mount| send(mount).schedule_background_upload } # rubocop:disable GitlabSecurity/PublicSend
  after_commit_queue.rb:51:in `instance_eval'
    self.instance_eval(&action)
  after_commit_queue.rb:51:in `_run_after_commit_queue'
    self.instance_eval(&action)
...
(179 additional frame(s) were not displayed)

NoMethodError: undefined method `schedule_background_upload' for nil:NilClass