Error when viewing page 2 or later of ElasticSearch search results

https://sentry.gitlab.net/gitlab/staginggitlabcom/issues/810154/

NoMethodError: undefined method `-' for "2":String
Did you mean?  -@
  gitlab/elastic/search_results.rb:59:in `eager_load'
    offset: per_page * (page - 1)
  gitlab/metrics/instrumentation.rb:161:in `block in eager_load'
    .measure { super }
  gitlab/metrics/method_call.rb:36:in `measure'
    retval = yield
  gitlab/metrics/instrumentation.rb:161:in `eager_load'
    .measure { super }
  gitlab/elastic/search_results.rb:28:in `objects'
    eager_load(projects, page, eager: [:route, :namespace])
...
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NoMethodError: undefined method `-' for "2":String
Did you mean?  -@