WIP: Debugging ERROR: TypeError{} - experiment1

What does this MR do?

Reproduces on latest master (Vue 2.5.1)

ERROR: TypeError{}

See experiment2 that is based on an old master with Vue 2.2.6, https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/15777

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Created for https://gitlab.com/gitlab-org/gitlab-ce/issues/37619#note_50422859

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Closes #37619 (closed)