Repositories fail to push when they contain a path lock or a push rule

https://sentry.gitlab.net/gitlab/gitlabcom/issues/587090/

TypeError: Invalid argument for string field.
  gitlab/gitaly_client/ref_service.rb:69:in `initialize'
    request = Gitaly::ListNewCommitsRequest.new(
  gitlab/gitaly_client/ref_service.rb:69:in `new'
    request = Gitaly::ListNewCommitsRequest.new(
  gitlab/gitaly_client/ref_service.rb:69:in `list_new_commits'
    request = Gitaly::ListNewCommitsRequest.new(
  gitlab/git/repository.rb:334:in `block in new_commits'
    gitaly_ref_client.list_new_commits(newrev)
  gitlab/git/wraps_gitaly_errors.rb:7:in `wrapped_gitaly_errors'
    yield block
...
(160 additional frame(s) were not displayed)

TypeError: Invalid argument for string field.