NoMethodError: undefined method `admin?' for nil:NilClass

https://sentry.gitlab.net/gitlab/gitlabcom/issues/1577975/?referrer=gitlab_plugin

NoMethodError: undefined method `admin?' for nil:NilClass
  api/groups.rb:94:in `present_groups'
    statistics: params[:statistics] && current_user.admin?
  api/groups.rb:125:in `block (2 levels) in <class:Groups>'
    present_groups params, groups
  grape/endpoint.rb:57:in `call'
    method.bind(endpoint_instance).call
  grape/endpoint.rb:57:in `block (2 levels) in generate_api_method'
    method.bind(endpoint_instance).call
  active_support/notifications.rb:182:in `instrument'
    yield payload if block_given?
...
(130 additional frame(s) were not displayed)

NoMethodError: undefined method `admin?' for nil:NilClass