Moving old CE issues produces Google::Protobuf::TypeError: Invalid argument for string field '' (given NilClass).

https://sentry.gitlab.net/gitlab/gitlabcom/issues/929357/

Google::Protobuf::TypeError: Invalid argument for string field '' (given NilClass).
  gitlab/gitaly_client/commit_service.rb:233:in `initialize'
    request = Gitaly::ListCommitsByOidRequest.new(repository: @gitaly_repo, oid: oids)
  gitlab/gitaly_client/commit_service.rb:233:in `new'
    request = Gitaly::ListCommitsByOidRequest.new(repository: @gitaly_repo, oid: oids)
  gitlab/gitaly_client/commit_service.rb:233:in `list_commits_by_oid'
    request = Gitaly::ListCommitsByOidRequest.new(repository: @gitaly_repo, oid: oids)
  gitlab/git/commit.rb:154:in `block in batch_by_oid'
    repo.gitaly_commit_client.list_commits_by_oid(oids)
  gitlab/git/wraps_gitaly_errors.rb:7:in `wrapped_gitaly_errors'
    yield block
...
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Google::Protobuf::TypeError: Invalid argument for string field '' (given NilClass).