Clicking "Play" button on an unplayable job (because there's no command/script) results in 404

Summary

Play button for "Deploy to Production" results in 404

193693550

Steps to reproduce

  1. Create a new project
  2. Use an example YML file like - https://gitlab.com/gitlab-org/gitlab-ce/snippets/32482 (includes deploy to production stage)
  3. Go to pipeline
  4. Click "Play" button and select "Deploy to production"
  5. /builds/:id/play is loaded
  6. Results in 404

//cc @ayufan @zj

ZD: https://gitlab.zendesk.com/agent/tickets/47065/events