[Regression] QEventLoopLocker causes application to quit even with open windows

#include <QApplication>
#include <QUrl>
#include <QTimer>
#include <QFileDialog>
#include <QWidget>

int main(int argc, char *argv[]) {
    // Without this (i.e. GTK file dialog), doesn't reproduce
    qputenv("QT_QPA_PLATFORMTHEME", QByteArray("kde"));

    QApplication app(argc, argv);
    
    // If there is no widget, reproduces always.
    // If there is a widget, setQuitOnLastWindowClosed(false)
    // (sic!) is needed to reproduce.
    app.setQuitOnLastWindowClosed(false);
    QWidget w;
    w.show();
    
    // Calling this directly before main loop runs -> doesn't reproduce
    QTimer::singleShot(0, []() { QFileDialog::getOpenFileName(); });
    
    return app.exec();
}

diff --git i/src/corelib/kernel/qcoreapplication.cpp w/src/corelib/kernel/qcoreapplication.cpp
index 1ce2642cf2..8d6d91cc2e 100644
--- i/src/corelib/kernel/qcoreapplication.cpp
+++ w/src/corelib/kernel/qcoreapplication.cpp
@@ -108,6 +108,7 @@
 #include <algorithm>
 #include <memory>
 #include <string>
+#include <csignal>
 
 QT_BEGIN_NAMESPACE
 
@@ -1650,6 +1651,9 @@ QCoreApplicationPrivate::QPostEventListLocker QCoreApplicationPrivate::lockThrea
 */
 void QCoreApplication::postEvent(QObject *receiver, QEvent *event, int priority)
 {
+    if (event->type() == QEvent::Quit) {
+        std::raise(SIGTRAP);
+    }
     Q_ASSERT_X(event, "QCoreApplication::postEvent", "Unexpected null event");
 
     Q_TRACE_SCOPE(QCoreApplication_postEvent, receiver, event, event->type());

#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=5, no_tid=no_tid@entry=0) at pthread_kill.c:44
#1  0x00007ffff78ab393 in __pthread_kill_internal (signo=5, threadid=<optimized out>) at pthread_kill.c:78
#2  0x00007ffff785a6c8 in __GI_raise (sig=5) at ../sysdeps/posix/raise.c:26
#3  0x00007ffff5964233 in QCoreApplication::postEvent(QObject*, QEvent*, int) () at /usr/lib/libQt6Core.so.6
#4  0x00007ffff596e731 in QEventLoopLocker::~QEventLoopLocker() () at /usr/lib/libQt6Core.so.6
#5  0x00007fffd29a1897 in KJobPrivate::~KJobPrivate (this=0x555557a01310, this=<optimized out>) at /usr/src/debug/kcoreaddons/kcoreaddons-6.1.0/src/lib/jobs/kjob.cpp:26
#6  0x00007fffd29a193e in KCompositeJobPrivate::~KCompositeJobPrivate (this=0x555557a01310, this=<optimized out>) at /usr/src/debug/kcoreaddons/kcoreaddons-6.1.0/src/lib/jobs/kcompositejob.cpp:18
#7  0x00007fffd29ab614 in std::default_delete<KJobPrivate>::operator() (__ptr=<optimized out>, this=<optimized out>) at /usr/include/c++/13.2.1/bits/unique_ptr.h:93
#8  std::unique_ptr<KJobPrivate, std::default_delete<KJobPrivate> >::~unique_ptr (this=0x55555797f8f0, this=<optimized out>) at /usr/include/c++/13.2.1/bits/unique_ptr.h:404
#9  KJob::~KJob (this=0x55555797f8e0, this=<optimized out>) at /usr/src/debug/kcoreaddons/kcoreaddons-6.1.0/src/lib/jobs/kjob.cpp:51
#10 0x00007fffd2f9b6fe in KIO::ListJob::~ListJob (this=0x55555797f8e0, this=<optimized out>) at /usr/src/debug/kio/kio-6.1.0/src/core/listjob.cpp:82
#11 0x00007ffff59a9218 in QObject::event(QEvent*) () at /usr/lib/libQt6Core.so.6
#12 0x00007ffff237bcdc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib/libQt6Widgets.so.6
...
#23 0x00007ffff5968ec4 in QCoreApplication::exec() () at /usr/lib/libQt6Core.so.6