Crash in QQmlContextPrivate::dropDestroyedQObject due to null IdentifierTable [regression in Qt 5.14]

Thread 1 "kscreenlocker_g" received signal SIGSEGV, Segmentation fault.
0x00007f40175a3d81 in QV4::IdentifierTable::insertString (this=0x0, s=...)
    at /d/qt/5/kde/qtdeclarative/src/qml/jsruntime/qv4identifiertable.cpp:145
145         uint idx = hash % alloc;
#0  0x00007f40175a3d81 in QV4::IdentifierTable::insertString (this=0x0, s=...)
    at /d/qt/5/kde/qtdeclarative/src/qml/jsruntime/qv4identifiertable.cpp:145
#1  0x00007f40175a4669 in QV4::IdentifierTable::asPropertyKey (this=0x0, s=...)
    at /d/qt/5/kde/qtdeclarative/src/qml/jsruntime/qv4identifiertable.cpp:283
#2  0x00007f40175a2d27 in QV4::IdentifierHash::lookup (this=0x5647136d0a18, str=...)
    at /d/qt/5/kde/qtdeclarative/src/qml/jsruntime/qv4identifier.cpp:155
#3  0x00007f4017762297 in QV4::IdentifierHash::value (this=0x5647136d0a18, str=...)
    at ../../include/QtQml/5.14.0/QtQml/private/../../../../../../../qtdeclarative/src/qml/jsruntime/qv4identifier_p.h:159
#4  0x00007f40177607ef in QQmlContextPrivate::dropDestroyedQObject (this=0x5647136d0960, name=..., destroyed=0x564713913480)
    at /d/qt/5/kde/qtdeclarative/src/qml/qml/qqmlcontext.cpp:535
#5  0x00007f401775fbb4 in QQmlContext::<lambda(QObject*)>::operator()(QObject *) const (__closure=0x5647136061a0, 
    destroyed=0x564713913480) at /d/qt/5/kde/qtdeclarative/src/qml/qml/qqmlcontext.cpp:323
#6  0x00007f40177620b2 in QtPrivate::FunctorCall<QtPrivate::IndexesList<0>, QtPrivate::List<QObject*>, void, QQmlContext::setContextProperty(const QString&, const QVariant&)::<lambda(QObject*)> >::call(QQmlContext::<lambda(QObject*)> &, void **) (f=..., 
    arg=0x7ffdd0619860) at /d/qt/5/kde/build/qtbase/include/QtCore/../../../../qtbase/src/corelib/kernel/qobjectdefs_impl.h:146
#7  0x00007f4017762082 in QtPrivate::Functor<QQmlContext::setContextProperty(const QString&, const QVariant&)::<lambda(QObject*)>, 1>::call<QtPrivate::List<QObject*>, void>(QQmlContext::<lambda(QObject*)> &, void *, void **) (f=..., arg=0x7ffdd0619860)
    at /d/qt/5/kde/build/qtbase/include/QtCore/../../../../qtbase/src/corelib/kernel/qobjectdefs_impl.h:256
#8  0x00007f4017762050 in QtPrivate::QFunctorSlotObject<QQmlContext::setContextProperty(const QString&, const QVariant&)::<lambda(QObject*)>, 1, QtPrivate::List<QObject*>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void **, bool *) (
    which=1, this_=0x564713606190, r=0x5647136d0940, a=0x7ffdd0619860, ret=0x0)
    at /d/qt/5/kde/build/qtbase/include/QtCore/../../../../qtbase/src/corelib/kernel/qobjectdefs_impl.h:439
#9  0x00007f4015f77211 in QtPrivate::QSlotObjectBase::call (this=0x564713606190, r=0x5647136d0940, a=0x7ffdd0619860)
    at ../../include/QtCore/../../../../qtbase/src/corelib/kernel/qobjectdefs_impl.h:394
#10 0x00007f4015fb4e20 in doActivate<false> (sender=0x564713913480, signal_index=0, argv=0x7ffdd0619860)
    at /d/qt/5/kde/qtbase/src/corelib/kernel/qobject.cpp:3870
#11 0x00007f4015faecbb in QMetaObject::activate (sender=0x564713913480, m=0x7f401652cc20 <QObject::staticMetaObject>, 
    local_signal_index=0, argv=0x7ffdd0619860) at /d/qt/5/kde/qtbase/src/corelib/kernel/qobject.cpp:3929
#12 0x00007f4015fb197f in QObject::destroyed (this=0x564713913480, _t1=0x564713913480) at .moc/moc_qobject.cpp:219
#13 0x00007f4015fa7ee3 in QObject::~QObject (this=0x564713913480, __in_chrg=<optimized out>)
    at /d/qt/5/kde/qtbase/src/corelib/kernel/qobject.cpp:1017
#14 0x00007f4018297f49 in QQuickItem::~QQuickItem (this=0x564713913480, __in_chrg=<optimized out>)
    at /d/qt/5/kde/qtdeclarative/src/quick/items/qquickitem.cpp:2383
#15 0x00007f4004b97996 in QQuickControl::~QQuickControl (this=0x564713913480, __in_chrg=<optimized out>)
    at /d/qt/5/kde/qtquickcontrols2/src/quicktemplates2/qquickcontrol.cpp:932
#16 0x00007f4004bf5b07 in QQuickStackView::~QQuickStackView (this=0x564713913480, __in_chrg=<optimized out>)
    at /d/qt/5/kde/qtquickcontrols2/src/quicktemplates2/qquickstackview.cpp:385
#17 0x00007f3fe7dce4b9 in QQmlPrivate::QQmlElement<QQuickStackView>::~QQmlElement (this=0x564713913480, 
    __in_chrg=<optimized out>)
    at /d/qt/5/kde/build/qtdeclarative/include/QtQml/../../../../qtdeclarative/src/qml/qml/qqmlprivate.h:110
#18 0x00007f3fe7dce4da in QQmlPrivate::QQmlElement<QQuickStackView>::~QQmlElement (this=0x564713913480, 
    __in_chrg=<optimized out>)
    at /d/qt/5/kde/build/qtdeclarative/include/QtQml/../../../../qtdeclarative/src/qml/qml/qqmlprivate.h:110
#19 0x00007f401932dfcc in KDeclarative::QmlObjectPrivate::~QmlObjectPrivate (this=0x564713913ea0, __in_chrg=<optimized out>)
    at /d/kde/src/5/frameworks/kdeclarative/src/kdeclarative/qmlobject.cpp:71
#20 KDeclarative::QmlObject::~QmlObject (this=0x564713917c10, __in_chrg=<optimized out>)
    at /d/kde/src/5/frameworks/kdeclarative/src/kdeclarative/qmlobject.cpp:199
#21 0x00007f401932ebd9 in KDeclarative::QmlObjectSharedEngine::~QmlObjectSharedEngine (this=0x564713917c10, 
    __in_chrg=<optimized out>) at /d/kde/src/5/frameworks/kdeclarative/src/kdeclarative/qmlobjectsharedengine.cpp:76
#22 0x00007f4015fa9e67 in QObjectPrivate::deleteChildren (this=0x5647135003d0)
    at /d/qt/5/kde/qtbase/src/corelib/kernel/qobject.cpp:2123
#23 0x00007f4015fa8398 in QObject::~QObject (this=0x56471351a3e0, __in_chrg=<optimized out>)
    at /d/qt/5/kde/qtbase/src/corelib/kernel/qobject.cpp:1107
#24 0x00007f40166a9964 in QWindow::~QWindow (this=0x56471351a3e0, __in_chrg=<optimized out>)
    at /d/qt/5/kde/qtbase/src/gui/kernel/qwindow.cpp:214
#25 0x00007f40182c9a05 in QQuickWindow::~QQuickWindow (this=0x56471351a3e0, __in_chrg=<optimized out>)
    at /d/qt/5/kde/qtdeclarative/src/quick/items/qquickwindow.cpp:1400
#26 0x00007f401ac864a9 in KQuickAddons::QuickViewSharedEngine::~QuickViewSharedEngine (this=0x56471351a3e0, 
    __in_chrg=<optimized out>) at /d/kde/src/5/frameworks/kdeclarative/src/quickaddons/quickviewsharedengine.cpp:149
#27 0x00005647122c3e4f in qDeleteAll<QList<KQuickAddons::QuickViewSharedEngine*>::const_iterator> (end=..., begin=...)
    at /d/qt/5/inst/include/QtCore/qalgorithms.h:320
#28 qDeleteAll<QList<KQuickAddons::QuickViewSharedEngine*> > (c=...) at /d/qt/5/inst/include/QtCore/qalgorithms.h:328
#29 ScreenLocker::UnlockApp::~UnlockApp (this=0x7ffdd0619e80, __in_chrg=<optimized out>)
    at /d/kde/src/5/kde/workspace/kscreenlocker/greeter/greeterapp.cpp:147
#30 0x00005647122bfcc1 in main (argc=<optimized out>, argv=<optimized out>)
    at /d/kde/src/5/kde/workspace/kscreenlocker/greeter/main.cpp:87