Gitlab::Elastic::Indexer::Error: Indexing commits..

https://sentry.gitlap.com/gitlab/gitlabcom/issues/10170/

Gitlab::Elastic::Indexer::Error: Indexing commits.../opt/gitlab/embedded/service/gem/ruby/2.3.0/gems/rugged-0.24.0/lib/rugged/repository.rb:17:in `head': Reference 'refs/heads/master' not found (Rugged::ReferenceError)
	from /opt/gitlab/embedded/service/gem/ruby/2.3.0/gems/rugged-0.24.0/lib/rugged/repository.rb:17:in `last_commit'
	from /opt/gitlab/embedded/service/gem/ruby/2.3.0/gems/gitlab-elasticsearch-git-0.0.17/lib/elasticsearch/git/repository.rb:185:in `index_commits'
	from /opt/gitlab/embedded/service/gitlab-rails/bin/elastic_repo_indexer:48:in `<main>'

  lib/gitlab/elastic/indexer.rb:33:in `run'
    raise Error, output unless status.zero?
  app/workers/elastic_commit_indexer_worker.rb:13:in `perform'
    indexer.run(
  lib/gitlab/sidekiq_middleware/request_store_middleware.rb:6:in `call'
    yield
  lib/gitlab/sidekiq_middleware/memory_killer.rb:17:in `call'
    yield
  lib/gitlab/sidekiq_middleware/arguments_logger.rb:6:in `call'
    yield
...
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