NoMethodError: undefined method `members' for nil:NilClass

Received error when attempting to view Group Billing page of a GitLab.com account.

https://sentry.gitlab.net/gitlab/gitlabcom/issues/914258/

NoMethodError: undefined method `members' for nil:NilClass
  admin/groups_controller.rb:19:in `show'
    @group.members.order("access_level DESC").page(params[:members_page]))
  action_controller/metal/basic_implicit_render.rb:6:in `send_action'
    super.tap { default_render unless performed? }
  abstract_controller/base.rb:194:in `process_action'
    send_action(method_name, *args)
  action_controller/metal/rendering.rb:30:in `process_action'
    super
  abstract_controller/callbacks.rb:42:in `block in process_action'
    super
...
(117 additional frame(s) were not displayed)

NoMethodError: undefined method `members' for nil:NilClass