fwbuilder crashes when trying to create almost any type of new object

To reproduce:
* start fwbuilder without any arguments
* click "New Object"
* click any type of object, e.g. "New Library"
* fwbuilder will segfault

Here is the stack trace:
(gdb) where
#0 0x000055555571115e in ?? ()
#1 0x000055555571cc73 in ?? ()
#2 0x0000555555720fc3 in ?? ()
#3 0x00005555559f3825 in ?? ()
#4 0x00007ffff6a49a88 in ?? () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#5 0x00007ffff76a8b86 in QAction::triggered(bool) () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#6 0x00007ffff76ab89c in QAction::activate(QAction::ActionEvent) () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#7 0x00007ffff78355d2 in ?? () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#8 0x00007ffff783d199 in ?? () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#9 0x00007ffff76f217e in QWidget::event(QEvent*) () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#10 0x00007ffff76af6b3 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#11 0x00007ffff76b72e4 in QApplication::notify(QObject*, QEvent*) () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#12 0x00005555559e2dfc in ?? ()
#13 0x00007ffff6a1216a in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#14 0x00007ffff76b5dc7 in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool, bool) () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#15 0x00007ffff770c4b3 in ?? () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#16 0x00007ffff770ec45 in ?? () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#17 0x00007ffff76af6b3 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#18 0x00005555559e2dfc in ?? ()
#19 0x00007ffff6a1216a in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#20 0x00007ffff6fa8257 in QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent*) () from /lib/x86_64-linux-gnu/libQt5Gui.so.5
#21 0x00007ffff6f7d9bc in QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5Gui.so.5
#22 0x00007ffff2d64b9e in ?? () from /lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#23 0x00007ffff55258bb in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#24 0x00007ffff5578f08 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#25 0x00007ffff5523003 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#26 0x00007ffff6a6b548 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#27 0x00007ffff6a10a9b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#28 0x00007ffff6a19024 in QCoreApplication::exec() () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#29 0x00005555556744cf in ?? ()
#30 0x00007ffff6324fd0 in __libc_start_call_main (main=main@entry=0x5555556736d3, argc=argc@entry=1, argv=argv@entry=0x7fffffffdd08) at ../sysdeps/nptl/libc_start_call_main.h:58
#31 0x00007ffff632507d in __libc_start_main_impl (main=0x5555556736d3, argc=1, argv=0x7fffffffdd08, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffdcf8) at ../csu/libc-start.c:409
#32 0x00005555556735de in ?? ()

Details:
Package version: 5.3.7-4.1build2
OS: VERSION="21.10 (Impish Indri)"