[Rails5] undefined method `first' for nil:NilClass

Note: add rails5 to a branch name to trigger rails5 specific CI jobs.

https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/74548955

  7) Gitlab::Auth::UserAuthFinders#find_user_from_feed_token when the request format is empty the method call does not modify the original value
     Failure/Error: current_request.path.ends_with?('.atom') || current_request.format.atom?

     NoMethodError:
       undefined method `first' for nil:NilClass
     # ./lib/gitlab/auth/user_auth_finders.rb:111:in `rss_request?'
     # ./lib/gitlab/auth/user_auth_finders.rb:29:in `find_user_from_feed_token'
     # ./spec/lib/gitlab/auth/user_auth_finders_spec.rb:104:in `block (4 levels) in <top (required)>'