ActionView::Template::Error: undefined method `total_count' for []:Array

Created by @rymai.

https://sentry.gitlap.com/gitlab/gitlabcom/issues/13630/

NoMethodError: undefined method `total_count' for []:Array
  lib/gitlab/elastic/project_search_results.rb:50:in `commits_count'
    @commits_count ||= commits.total_count
  lib/gitlab/metrics/instrumentation.rb:155:in `block in commits_count'
    trans.method_call_for(#{label.to_sym.inspect}).measure { super }
  lib/gitlab/metrics/method_call.rb:23:in `measure'
    retval = yield
  lib/gitlab/metrics/instrumentation.rb:155:in `commits_count'
    trans.method_call_for(#{label.to_sym.inspect}).measure { super }
  app/views/search/_category.html.haml:37:in `block in _app_views_search__category_html_haml__1971640003665015742_70328335303060'
    = @search_results.commits_count
...
(148 additional frame(s) were not displayed)

ActionView::Template::Error: undefined method `total_count' for []:Array

/cc @vsizov