Editor crashes on close when preview is left on

Steps to reproduce:

• Launch editor, open any presentation (e.g. kria cluster demo)
• From editor launch preview (doesn't matter which runtime version)
• Close editor with preview window open
• Close preview
• Segmentation fault occurs in CCore::GetDoc

Call stack below:

1 CCore::GetDoc Core.cpp 78 0xa3fc7c
2 CPreviewHelper::cleanupProcess PreviewHelper.cpp 174 0xe45fd4
3 CPreviewHelper::DoPreviewViaConfig(Q3DStudio::CBuildConfiguration *, QString const&, CPreviewHelper::EExecMode, QString const&, RemoteDeploymentSender *)::$_2::operator()() const PreviewHelper.cpp 212 0xe4672f
4 QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, CPreviewHelper::DoPreviewViaConfig(Q3DStudio::CBuildConfiguration *, QString const&, CPreviewHelper::EExecMode, QString const&, RemoteDeploymentSender *)::$_2>::call(CPreviewHelper::DoPreviewViaConfig(Q3DStudio::CBuildConfiguration *, QString const&, CPreviewHelper::EExecMode, QString const&, RemoteDeploymentSender *)::$_2&, void * *) qobjectdefs_impl.h 146 0xe466f9
5 QtPrivate::Functor<CPreviewHelper::DoPreviewViaConfig(Q3DStudio::CBuildConfiguration *, QString const&, CPreviewHelper::EExecMode, QString const&, RemoteDeploymentSender *)::$_2, 0>::call<QtPrivate::List<>, void>(CPreviewHelper::DoPreviewViaConfig(Q3DStudio::CBuildConfiguration *, QString const&, CPreviewHelper::EExecMode, QString const&, RemoteDeploymentSender *)::$_2&, void *, void * *) qobjectdefs_impl.h 256 0xe466d1
6 QtPrivate::QFunctorSlotObject<CPreviewHelper::DoPreviewViaConfig(Q3DStudio::CBuildConfiguration *, QString const&, CPreviewHelper::EExecMode, QString const&, RemoteDeploymentSender *)::$_2, 0, QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void * *, bool *) qobjectdefs_impl.h 439 0xe4667d
7 QMetaObject::activate(QObject *, int, int, void * *) 0x7ffff33e7f26
8 QCoreApplication::aboutToQuit(QCoreApplication::QPrivateSignal) 0x7ffff33bb527
9 QCoreApplicationPrivate::execCleanup() 0x7ffff33bf18b
10 QCoreApplication::exec() 0x7ffff33c34f8
11 CStudioApp::runApplication StudioApp.cpp 727 0xc8c47a
12 CStudioApp::blankRunApplication StudioApp.cpp 659 0xc898fe
13 CStudioApp::run StudioApp.cpp 404 0xc8843e
14 main StudioApp.cpp 166 0xc86f2b