Dangerfile CI job fails with "invalid `Dangerfile` file"

https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/15436#note_207900971

It seems that test automation eng role is nil - https://gitlab.com/gitlab-org/gitlab-ee/blob/master/lib/gitlab/danger/teammate.rb#L42, perhaps we should handle nil values too.

Ci job: https://gitlab.com/gitlab-org/gitlab-ee/-/jobs/281414915

/builds/gitlab-org/gitlab-ee/lib/gitlab/danger/teammate.rb:42:in `has_capability?':  (Danger::DSLError)
[!] Invalid `Dangerfile` file: 
[!] Invalid `Dangerfile` file: undefined method `downcase' for nil:NilClass
 #  from danger/roulette/Dangerfile:44
 #  -------------------------------------------
 #        team.select do |member|
 >          member.public_send(kind, project, category, labels) # rubocop:disable GitlabSecurity/PublicSend
 #        end
 #  -------------------------------------------

 #  from danger/roulette/Dangerfile:44
 #  -------------------------------------------
 #   >   #  
 #  -------------------------------------------
	from /builds/gitlab-org/gitlab-ee/lib/gitlab/danger/teammate.rb:25:in `reviewer?'
	from danger/roulette/Dangerfile:44:in `public_send'
	from danger/roulette/Dangerfile:44:in `block (2 levels) in spin_for_category'