JenkinsDeprecatedService: NoMethodError: undefined method `attributes' for nil:NilClass

https://sentry.gitlab.net/gitlab/gitlabcom/issues/218179/

NoMethodError: undefined method `attributes' for nil:NilClass
  jenkins_deprecated_service.rb:105:in `read_commit_status'
    src = Nokogiri.parse(response).css('img.build-caption-status-icon,.build-caption>img').first.attributes['src'].value
  jenkins_deprecated_service.rb:83:in `calculate_reactive_cache'
    { commit_status: read_commit_status(sha, ref) }
  reactive_caching.rb:96:in `block (2 levels) in exclusively_update_reactive_cache!'
    new_value = calculate_reactive_cache(*args)
  reactive_caching.rb:141:in `enqueuing_update'
    yield
  gitlab/metrics/instrumentation.rb:159:in `block in enqueuing_update'
    .measure { super }
...
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NoMethodError: undefined method `attributes' for nil:NilClass