Zoekt search returns 400 http status code for some searches

Summary

some zoekt searches are generating 400 http response codes from the zoekt web server

Steps to reproduce

Unknown

What is the current bug behavior?

What is the expected correct behavior?

Relevant logs and/or screenshots

kibana for zoekt 400 errors from webserver side: https://log.gprd.gitlab.net/app/r/s/pMr4z

kibana (internal) for zoekt client 400 errors: https://log.gprd.gitlab.net/app/r/s/Fw1Hs

{"Error":"error parsing regexp: missing argument to repetition operator: `*`"}

Possible fixes