Error 500 loading projects page: Undefined method `cache_key' for nil:NilClass

https://sentry.gitlap.com/gitlab/gitlabcom/issues/108133/

NoMethodError: undefined method `cache_key' for nil:NilClass
  app/helpers/projects_helper.rb:215:in `project_list_cache_key'
    project.route.cache_key,
  app/views/shared/projects/_project.html.haml:11:in `_app_views_shared_projects__project_html_haml___2428168726327152414_69910506259360'
    - cache_key = project_list_cache_key(project)
  app/views/shared/projects/_list.html.haml:19:in `block in _app_views_shared_projects__list_html_haml__961100400681920291_69910519362120'
    = render "shared/projects/project", project: project, skip_namespace: skip_namespace,
  app/views/shared/projects/_list.html.haml:17:in `_app_views_shared_projects__list_html_haml__961100400681920291_69910519362120'
    - projects.each_with_index do |project, i|
  app/controllers/application_controller.rb:254:in `view_to_html_string'
    render_to_string(
...
(163 additional frame(s) were not displayed)

ActionView::Template::Error: undefined method `cache_key' for nil:NilClass

ActionView::Template::Error: undefined method `cache_key' for nil:NilClass