dev-util/perf: fix version detection logic

Fix an empty version in the `perf version` output.

BUG=b/318857411
TEST=presubmit
RELEASE_NOTE=None

cos-patch: lts-refresh
Change-Id: I22eb1d3d1782e9990cf81815b5e76a1f71aa4953
Reviewed-on: https://cos-review.googlesource.com/c/third_party/overlays/chromiumos-overlay/+/68355
Reviewed-by: Kevin Berry <kpberry@google.com>
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Tested-by: Oleksandr Tymoshenko <ovt@google.com>
2 files changed