Render 404 if there is no project for old CI status badge

app/controllers/ci/projects_controller.rb

@@ -17,6 +17,7 @@ module Ci
     # with projects migrated from GitLab CI.
     #
     def badge
+      return render_404 unless @project
       image = Ci::ImageForBuildService.new.execute(@project, params)
       send_file image.path, filename: image.name, disposition: 'inline', type:"image/svg+xml"
     end