git: openjdk/loom: fibers: JFR: map the vthread default name onto the empty string instead of null

[duke]

Changeset: 686e2445
Author:    mgronlun <markus.gronlund at oracle.com>
Date:      2022-03-20 13:18:13 +0000
URL:       https://git.openjdk.java.net/loom/commit/686e2445a65144bf6d219bc18bee55e7507837fa

JFR: map the vthread default name onto the empty string instead of null

! src/hotspot/share/jfr/recorder/checkpoint/types/jfrThreadState.cpp
! src/hotspot/share/jfr/recorder/checkpoint/types/jfrThreadState.hpp
! src/hotspot/share/jfr/recorder/checkpoint/types/jfrType.cpp
! src/hotspot/share/jfr/recorder/checkpoint/types/jfrType.hpp
! src/hotspot/share/jfr/support/jfrIntrinsics.cpp
! src/hotspot/share/jfr/support/jfrThreadLocal.cpp
! src/hotspot/share/jfr/writers/jfrWriterHost.hpp
! src/hotspot/share/jfr/writers/jfrWriterHost.inline.hpp
! src/hotspot/share/opto/library_call.cpp
! src/jdk.jfr/share/classes/jdk/jfr/internal/EventWriter.java
! test/jdk/jdk/jfr/threading/TestManyVirtualThreads.java
! test/jdk/jdk/jfr/threading/TestNestedVirtualThreads.java