git: openjdk/jdk-sandbox: parttimenerd_jfr_cpu_time_sampler3: Reset stacktraces from samples without threads

[duke]

Changeset: 88bff4c0
Author:    Johannes Bechberger <johannes.bechberger at sap.com>
Date:      2024-06-24 13:03:45 +0000
URL:       https://git.openjdk.org/jdk-sandbox/commit/88bff4c040ffcb5eb536513fbfff901ca7cde0bb

Reset stacktraces from samples without threads

! src/hotspot/share/jfr/periodic/sampling/jfrCPUTimeThreadSampler.cpp