Crash/race in destroying QSoundEffect

QSoundEffect has a race when an application is destroyed soon after its initialization (which can manifest in multiple different failures/crashes). Whilst not so much of a problem for a long running application, it manifests more frequently in qmlplugindump where it crashes in modules that use QSoundEffect (since object instances are short-lived there).

The crux seems to be that QSample::load is queued for execution on its own thread, which conflicts with creating/using various networking classes which don't function when the application is shutting down.

Attached is a small, artificial example, which manifests in a crash roughly 10% of the time.

Some example results:

for i in {1..10}; do ./test; done

QObject::connect: Cannot connect (null)::configurationAdded(QNetworkConfiguration) to QNetworkConfigurationManager::configurationAdded(QNetworkConfiguration)
QObject::connect: Cannot connect (null)::configurationRemoved(QNetworkConfiguration) to QNetworkConfigurationManager::configurationRemoved(QNetworkConfiguration)
QObject::connect: Cannot connect (null)::configurationChanged(QNetworkConfiguration) to QNetworkConfigurationManager::configurationChanged(QNetworkConfiguration)
QObject::connect: Cannot connect (null)::onlineStateChanged(bool) to QNetworkConfigurationManager::onlineStateChanged(bool)
QObject::connect: Cannot connect (null)::configurationUpdateComplete() to QNetworkConfigurationManager::updateCompleted()
Segmentation fault (core dumped)

for i in {1..10}; do ./test; done

QEventLoop: Cannot be used without QApplication
Segmentation fault (core dumped)

for i in {1..30}; do ./test; done

QMutex: destroying locked mutex
Segmentation fault (core dumped){{}}