Commit search breaks for some URLs on gitlab-ce project

Description of the problem

• https://gitlab.com/search?project_id=13083&scope=commits&search=%27lower breaks
• https://gitlab.com/search?project_id=13083&scope=commits&search=flower%27lower breaks
• https://gitlab.com/search?project_id=13083&scope=commits&search=%27flower doesn't break
• https://gitlab.com/search?project_id=1350099&scope=commits&search=%27lower doesn't break

Which Group/Project (with full path) is experiencing the issue?

only https://gitlab.com/gitlab-org/gitlab-ce/

Approximate date/time when the error occurred.

every time

Describe what you were doing right before the issue occurred.

searching a commit

---

Maybe caused by https://gitlab.com/gitlab-org/gitlab-ce/issues/20063

Possibility of injection involved (yet unlikely), therefore confidential.

cc @stanhu