Merge branch 'sh-fix-division-by-zero' into 'master'

Avoid division by zero in Elasticsearch rate calculator

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/172642



Merged-by: Marc Shaw <mshaw@gitlab.com>
Approved-by: Changzheng Liu <cliu@gitlab.com>
Approved-by: Marc Shaw <mshaw@gitlab.com>
Co-authored-by: Stan Hu <stanhu@gmail.com>