git: openjdk/jdk-sandbox: parttimenerd_jfr_cpu_time_sampler4: Fix is_empty

[duke]

Changeset: 400d416d
Branch: parttimenerd_jfr_cpu_time_sampler4
Author:    Johannes Bechberger <johannes.bechberger at sap.com>
Date:      2024-08-23 13:01:13 +0000
URL:       https://git.openjdk.org/jdk-sandbox/commit/400d416ddea8bcae5574c35416ab84c0939483a4

Fix is_empty

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