Description of problem:
As https://bugzilla.redhat.com/show_bug.cgi?id=2367096 explains:

> I attempted to use the "Print" modal, despite https://bugreports.qt.io/browse/QTBUG-135786.

Version-Release number of selected component:
khelpcenter-1:25.04.1-1.fc42

Additional info:
reporter:       libreport-2.17.15
type:           CCpp
reason:         khelpcenter killed by SIGABRT
journald_cursor: s=c1f108f1ef4e48808a377c0a73f168fc;i=4ff509;b=41a13c264475412bac2e146d26dc849a;m=18424db89;t=6356d1b95a78d;x=429b3bfba43ee5f0
executable:     /usr/bin/khelpcenter
cmdline:        /usr/bin/khelpcenter
cgroup:         0::/user.slice/user-1000.slice/user/app.slice/dbus-:1.2-org.kde.khelpcenter
rootdir:        /
uid:            1000
kernel:         6.14.6-300.fc42.x86_64
backtrace_rating: 4
crash_function: __syscall_cancel_arch
package:        khelpcenter-1:25.04.1-1.fc42

Truncated backtrace:
Thread no. 0 (78 frames)
 #0 __syscall_cancel_arch at ../sysdeps/unix/sysv/linux/x86_64/syscall_cancel.S:56
 #1 __internal_syscall_cancel at cancellation.c:49
 #2 __syscall_cancel at cancellation.c:75
 #3 __poll at ../sysdeps/unix/sysv/linux/poll.c:29
 #4 poll at /usr/include/bits/poll2.h:44
 #5 cups_dnssd_poll_cb at /usr/src/debug/cups-2.4.12-3.fc42.x86_64/cups/dest.c:2942
 #6 avahi_simple_poll_run at /usr/src/debug/avahi-0.9
 #7 avahi_simple_poll_iterate at /usr/src/debug/avahi-0.9
 #9 cups_enum_dests at /usr/src/debug/cups-2.4.12-3.fc42.x86_64/cups/dest.c:3800
 #10 cupsGetDests2 at /usr/src/debug/cups-2.4.12-3.fc42.x86_64/cups/dest.c:1704
 #11 QCupsPrinterSupport::staticDefaultPrintDeviceId at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/plugins/printsupport/cups/qcupsprintersupport.cpp:149
 #12 QCupsPrinterSupport::defaultPrintDeviceId at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/plugins/printsupport/cups/qcupsprintersupport.cpp:142
 #13 QPrinterInfo::defaultPrinter at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/printsupport/kernel/qprinterinfo.cpp:424
 #14 QPrinterPrivate::findValidPrinter at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/printsupport/kernel/qprinter.cpp:50
 #15 QPrinter::setOutputFormat at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/printsupport/kernel/qprinter.cpp:557
 #16 QUnixPrintWidgetPrivate::_q_printerChanged at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/printsupport/dialogs/qprintdialog_unix.cpp:1153
 #17 doActivate<false> at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobject.cpp:4150
 #18 QMetaObject::activate at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobject.cpp:4198
 #19 QMetaObject::activate<void, int> at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobjectdefs.h:306
 #20 QComboBox::currentIndexChanged at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/redhat-linux-build/src/widgets/Widgets_autogen/include/moc_qcombobox.cpp:367
 #21 QComboBoxPrivate::emitCurrentIndexChanged at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/itemmodels/qabstractitemmodel.h:130
 #22 QComboBoxPrivate::setCurrentIndex at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/widgets/qcombobox.cpp:2223
 #23 QComboBox::setCurrentIndex at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/widgets/qcombobox.cpp:2170
 #24 QtPrivate::QSlotObjectBase::call at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobjectdefs_impl.h:461
 #25 doActivate<false> at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobject.cpp:4138
 #26 QMetaObject::activate at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobject.cpp:4198
 #27 QMetaObject::activate<void, QModelIndex, int, int, QAbstractItemModel::QPrivateSignal> at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobjectdefs.h:306
 #28 QAbstractItemModel::rowsInserted at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/redhat-linux-build/src/corelib/Core_autogen/include/moc_qabstractitemmodel.cpp:688
 #29 QAbstractItemModel::endInsertRows at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/itemmodels/qabstractitemmodel.cpp:2914
 #30 QStandardItemModelPrivate::rowsInserted at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/gui/itemmodels/qstandarditemmodel.cpp:629
 #31 QStandardItemPrivate::insertRows at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/gui/itemmodels/qstandarditemmodel.cpp:501
 #32 QStandardItem::insertRow at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/gui/itemmodels/qstandarditemmodel.cpp:1605
 #33 QStandardItemModel::insertRow at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/gui/itemmodels/qstandarditemmodel.cpp:2684
 #35 QComboBox::insertItem at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/widgets/qcombobox.cpp:2336
 #37 QComboBox::addItem at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/widgets/qcombobox.h:220
 #38 QUnixPrintWidgetPrivate::updateWidget at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/printsupport/dialogs/qprintdialog_unix.cpp:1083
 #39 QPrintDialogPrivate::updateWidgets at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/printsupport/dialogs/qprintdialog_unix.cpp:930
 #40 QPrintDialog::setVisible at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/printsupport/dialogs/qprintdialog_unix.cpp:980
 #41 QDialog::exec at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/dialogs/qdialog.cpp:567
 #42 QPrintDialog::exec at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/printsupport/dialogs/qprintdialog_unix.cpp:987
 #43 PrintDoc::print at /usr/src/debug/khelpcenter-25.04.1-1.fc42.x86_64/printdoc.cpp:39
 #44 KHC::MainWindow::slotPrint at /usr/src/debug/khelpcenter-25.04.1-1.fc42.x86_64/mainwindow.cpp:431
 #45 KHC::MainWindow::qt_static_metacall at /usr/src/debug/khelpcenter-25.04.1-1.fc42.x86_64/redhat-linux-build/khelpcenter_autogen/include/moc_mainwindow.cpp:183
 #46 doActivate<false> at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobject.cpp:4150
 #47 QMetaObject::activate at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobject.cpp:4198
 #48 QMetaObject::activate<void, bool> at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobjectdefs.h:306
 #49 QAction::triggered at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/redhat-linux-build/src/gui/Gui_autogen/include/moc_qaction.cpp:372
 #50 QAction::activate at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/gui/kernel/qaction.cpp:1104
 #51 QMenuPrivate::activateCausedStack at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/widgets/qmenu.cpp:1410
 #52 QMenuPrivate::activateAction at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/widgets/qmenu.cpp:1492
 #53 QWidget::event at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/kernel/qwidget.cpp:9354
 #54 QApplicationPrivate::notify_helper at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/kernel/qapplication.cpp:3301
 #55 QApplication::notify at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/kernel/qapplication.cpp:2778
 #56 QCoreApplication::notifyInternal2 at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qcoreapplication.cpp:1106
 #57 QCoreApplication::sendSpontaneousEvent at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qcoreapplication.cpp:1560
 #58 QApplicationPrivate::sendMouseEvent at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/kernel/qapplication.cpp:2359
 #59 QWidgetWindow::handleMouseEvent at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/kernel/qwidgetwindow.cpp:577
 #60 QWidgetWindow::event at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/kernel/qwidgetwindow.cpp:292
 #61 QApplicationPrivate::notify_helper at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/kernel/qapplication.cpp:3301
 #62 QCoreApplication::notifyInternal2 at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qcoreapplication.cpp:1106
 #63 QCoreApplication::sendSpontaneousEvent at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qcoreapplication.cpp:1560
 #64 QGuiApplicationPrivate::processMouseEvent at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/gui/kernel/qguiapplication.cpp:2483
 #65 QWindowSystemInterface::sendWindowSystemEvents at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/gui/kernel/qwindowsysteminterface.cpp:1113
 #66 QWindowSystemInterface::flushWindowSystemEvents at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/gui/kernel/qwindowsysteminterface.cpp:1082
 #67 QObject::event at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qobject.cpp:1431
 #68 QApplicationPrivate::notify_helper at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/kernel/qapplication.cpp:3301
 #69 QCoreApplication::notifyInternal2 at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qcoreapplication.cpp:1106
 #70 QCoreApplication::sendEvent at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qcoreapplication.cpp:1546
 #71 QCoreApplicationPrivate::sendPostedEvents at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qcoreapplication.cpp:1879
 #72 postEventSourceDispatch at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qeventdispatcher_glib.cpp:246
 #74 g_main_context_dispatch_unlocked at ../glib/gmain.c:4249
 #75 g_main_context_iterate_unlocked at ../glib/gmain.c:4314
 #76 g_main_context_iteration at ../glib/gmain.c:4379
 #77 QEventDispatcherGlib::processEvents at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qeventdispatcher_glib.cpp:399
 #78 QEventLoop::exec at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/global/qflags.h:77
 #79 QCoreApplication::exec at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/corelib/kernel/qcoreapplication.cpp:1449
 #80 QGuiApplication::exec at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/gui/kernel/qguiapplication.cpp:1993
 #81 QApplication::exec at /usr/src/debug/qt6-qtbase-6.9.0-2.fc42.x86_64/src/widgets/kernel/qapplication.cpp:2568