Comment 0 for bug 1940589

This randomly happens when running tests on main (e.g. 2.4-alpha-767-g0774a046ca):

    Using host libthread_db library "/usr/lib/libthread_db.so.1".
    Core was generated by `/home/jan/Projects/mixxx/build/mixxx-test --gtest_filter=AdjustReplayGainTest.A'.
    Program terminated with signal SIGSEGV, Segmentation fault.
    #0 0x000055bd8e0236fb in SyncControl::slotControlPlay (this=0x55bd8f83dc30, play=0) at /home/jan/Projects/mixxx/src/engine/sync/synccontrol.cpp:385
    385 m_pEngineSync->notifyPlayingAudible(this, play > 0.0 && m_audible);
    [Current thread is 1 (Thread 0x7f8a57579640 (LWP 175095))]
    >>> bt
    #0 0x000055bd8e0236fb in SyncControl::slotControlPlay(double) (this=0x55bd8f83dc30, play=0) at /home/jan/Projects/mixxx/src/engine/sync/synccontrol.cpp:385
    #1 0x00007f8a6b6de75b in () at /usr/lib/libQt5Core.so.5
    #2 0x000055bd8df3c080 in ControlProxy::valueChanged(double) (this=<optimized out>, _t1=<optimized out>) at /home/jan/Projects/mixxx/build/mixxx-lib_autogen/include/moc_controlproxy.cpp:164
    #3 0x00007f8a6b6de75b in () at /usr/lib/libQt5Core.so.5
    #4 0x000055bd8df30965 in ControlDoublePrivate::valueChanged(double, QObject*) (this=this@entry=0x55bd8f7ee060, _t1=<optimized out>, _t1@entry=0, _t2=<optimized out>) at /home/jan/Projects/mixxx/build/mixxx-lib_autogen/include/moc_control.cpp:145
    #5 0x000055bd8df310ee in ControlDoublePrivate::setInner(double, QObject*) (this=0x55bd8f7ee060, value=0, pSender=<optimized out>) at /home/jan/Projects/mixxx/src/control/control.cpp:223
    #6 0x00007f8a6b6de75b in () at /usr/lib/libQt5Core.so.5
    #7 0x000055bd8df308f3 in ControlDoublePrivate::valueChangeRequest(double) (this=this@entry=0x55bd8f7ee060, _t1=<optimized out>) at /home/jan/Projects/mixxx/build/mixxx-lib_autogen/include/moc_control.cpp:152
    #8 0x000055bd8df31228 in ControlDoublePrivate::set(double, QObject*) (this=0x55bd8f7ee060, value=<optimized out>, pSender=0x55bd8f7edfc0) at /home/jan/Projects/mixxx/src/control/control.cpp:208
    #9 0x000055bd8dff8c16 in ControlObject::set(double) (value=<optimized out>, this=<optimized out>) at /home/jan/Projects/mixxx/src/control/controlobject.h:83
    #10 EngineBuffer::slotTrackLoading() (this=0x55bd8f7e5fe0) at /home/jan/Projects/mixxx/src/engine/enginebuffer.cpp:523
    #11 0x00007f8a6b6de75b in () at /usr/lib/libQt5Core.so.5
    #12 0x00007f8a6b6de75b in () at /usr/lib/libQt5Core.so.5
    #13 0x000055bd8dfcb260 in CachingReaderWorker::loadTrack(std::shared_ptr<Track> const&) (this=0x55bd8f7e9478, pTrack=std::shared_ptr<Track> (use count 5, weak count 0) = {...}) at /home/jan/Projects/mixxx/src/engine/cachingreader/cachingreaderworker.cpp:136
    #14 0x000055bd8dfcd2ad in CachingReaderWorker::run() (this=0x55bd8f7e9478) at /home/jan/Projects/mixxx/src/engine/cachingreader/cachingreaderworker.cpp:104
    #15 0x00007f8a6b4bbfef in () at /usr/lib/libQt5Core.so.5
    #16 0x00007f8a6afd6259 in start_thread () at /usr/lib/libpthread.so.0
    #17 0x00007f8a6aeff5e3 in clone () at /usr/lib/libc.so.6