Fix NPE with horse racing emoji check

What does this MR do?

• Fix NPE with horse racing emoji check

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

Sentry shows it reproducing on these pages but I am unable to reproduce, https://sentry.gitlap.com/gitlab/gitlabcom-clientside/issues/31095/

• https://gitlab.com/gitlab-org/gitlab-ce/issues/7889
• https://gitlab.com/gitlab-org/gitlab-ee/issues/91
• https://gitlab.com/gitlab-org/gitlab-ce/issues/18231
• https://gitlab.com/gitlab-org/gitlab-recipes/issues/57

I could see it happening with an empty (or just with whitespace) <gl-emoji></gl-emoji> which would originate from a BE markdown banzai issue. But I don't get that on those reproduction pages either. Perhaps a browser extension getting rid of content?

Why was this MR needed?

• JS error thrown in some situations, https://sentry.gitlap.com/gitlab/gitlabcom-clientside/issues/31095/

Does this MR meet the acceptance criteria?

• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #32587 (closed)