Flaky nil panic in tests

https://gitlab.com/gitlab-org/gitlab-workhorse/-/jobs/702281368

	/builds/gitlab-org/gitlab-workhorse/internal/gitaly/smarthttp.go:119 +0xd7
created by gitlab.com/gitlab-org/gitlab-workhorse/internal/gitaly.(*SmartHTTPClient).UploadPack
	/builds/gitlab-org/gitlab-workhorse/internal/gitaly/smarthttp.go:114 +0x256
FAIL	gitlab.com/gitlab-org/gitlab-workhorse	21.863s

It does not happen every time. It appears to happen on Go 1.13 only. ??