lxde/lxqt-panel: crash upon launching Firefox

gdb_backtrace.txt

#0  0x00007f3ce976f621 in QXcbWindow::mapToNative(QRect const&, QXcbScreen const*) const () from /usr/lib/libQt5XcbQpa.so.5
#1  0x00007f3ce9775d33 in QXcbWindow::setGeometry(QRect const&) () from /usr/lib/libQt5XcbQpa.so.5
#2  0x00007f3cf44b6b9c in QWidgetPrivate::setGeometry_sys(int, int, int, int, bool) () from /usr/lib/libQt5Widgets.so.5
#3  0x00007f3cf44b75f0 in QWidget::setGeometry(QRect const&) () from /usr/lib/libQt5Widgets.so.5
#4  0x00007f3cf449ee14 in QWidgetItem::setGeometry(QRect const&) () from /usr/lib/libQt5Widgets.so.5
#5  0x0000000000434b74 in LxQtPanelLayout::setItemGeometry(QLayoutItem*, QRect const&, bool) ()
#6  0x00000000004364b1 in LxQtPanelLayout::setGeometryHoriz(QRect const&) ()
#7  0x0000000000437435 in LxQtPanelLayout::setGeometry(QRect const&) ()
#8  0x00007f3cf449b15f in QLayoutPrivate::doResize(QSize const&) () from /usr/lib/libQt5Widgets.so.5
#9  0x00007f3cf449cda8 in QLayout::activate() () from /usr/lib/libQt5Widgets.so.5
#10 0x00007f3cf44be77d in QWidget::setVisible(bool) () from /usr/lib/libQt5Widgets.so.5
#11 0x0000000000474118 in ?? ()
#12 0x0000000000474497 in ?? ()
#13 0x000000000046adde in ?? ()
#14 0x000000000046b11b in ?? ()
#15 0x00007f3cf3561fea in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib/libQt5Core.so.5
#16 0x00007f3cf4be682c in ?? () from /usr/lib/libKF5WindowSystem.so.5
#17 0x00007f3cf35303ff in QAbstractEventDispatcher::filterNativeEvent(QByteArray const&, void*, long*) () from /usr/lib/libQt5Core.so.5
#18 0x00007f3ce975d2c4 in QXcbConnection::handleXcbEvent(xcb_generic_event_t*) () from /usr/lib/libQt5XcbQpa.so.5
#19 0x00007f3ce975e073 in QXcbConnection::processXcbEvents() () from /usr/lib/libQt5XcbQpa.so.5
#20 0x00007f3cf3562eb1 in QObject::event(QEvent*) () from /usr/lib/libQt5Core.so.5
#21 0x00007f3cf447c00c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQt5Widgets.so.5
#22 0x00007f3cf44814e6 in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQt5Widgets.so.5
#23 0x00007f3cf353389b in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQt5Core.so.5
#24 0x00007f3cf3535c96 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /usr/lib/libQt5Core.so.5
#25 0x00007f3cf3589e33 in ?? () from /usr/lib/libQt5Core.so.5
#26 0x00007f3cf63499fd in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#27 0x00007f3cf6349ce0 in ?? () from /usr/lib/libglib-2.0.so.0
#28 0x00007f3cf6349d8c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#29 0x00007f3cf358a23f in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#30 0x00007f3cf353126a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#31 0x00007f3cf353920c in QCoreApplication::exec() () from /usr/lib/libQt5Core.so.5
#32 0x00000000004269e4 in ?? ()
#33 0x00007f3cf2880790 in __libc_start_main () from /usr/lib/libc.so.6
#34 0x0000000000426f89 in _start ()