Bug 468592

SUMMARY
***
NOTE: If you are reporting a crash, please try to attach a backtrace with debug symbols.
See https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports
***
When opening the lesson configuration window, the program crashes with a segfault.

STEPS TO REPRODUCE
1. Open parley with `QT_QPA_PLATFORM=xcb parley` under wayland (not sure if this is relevant).
2. Click on "Learn" for any file.
3. Go to "lesson" -> "configure lesson" (in German: "Übung" -> "Übung einrichten")

OBSERVED RESULT
```
$ QT_QPA_PLATFORM=xcb parley
Expired words dropped their confidence:  0
Expired words dropped their confidence:  0
KEduVocKvtmlReader for kvtml version 1 files started.
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
Warning! Lesson order may be confused. Are all lessons in order in the file?
addLanguage(  0 ,  "de" ):  "German"
addLanguage(  1 ,  "es" ):  "Spanish"
Reading user defined tense description:  "Presente"
 Add tense:  "#1"  -  "Presente"
Reading user defined tense description:  "Participio"
 Add tense:  "#2"  -  "Participio"
Reading user defined tense description:  "Gerundio"
 Add tense:  "#3"  -  "Gerundio"
Reading user defined tense description:  "Pretérito perfecto"
 Add tense:  "#4"  -  "Pretérito perfecto"
Reading user defined tense description:  "Pretérito indefinido"
 Add tense:  "#5"  -  "Pretérito indefinido"
Reading user defined tense description:  "Futuro imperfecto"
 Add tense:  "#6"  -  "Futuro imperfecto"
Reading user defined tense description:  "Condicional simple"
 Add tense:  "#7"  -  "Condicional simple"
Reading user defined tense description:  "Imperativo"
 Add tense:  "#8"  -  "Imperativo"
Reading user defined tense description:  "Subjuntivo presente"
 Add tense:  "#9"  -  "Subjuntivo presente"
Expired words dropped their confidence:  0
Expired words dropped their confidence:  0
"<qt>Die Datei kann nicht geöffnet werden.<br /><b>file:http://vokabeln.kvtml</b></qt>"
Expired words dropped their confidence:  0
Expired words dropped their confidence:  0
Attempting to load .desktop at "/usr/share/parley/themes/theme_reference.desktop"
"Die Datei ~/.local/share/kvtml/143429-deutsch_niederlaendisch.kvtml kann nicht gesperrt werden."
kf.notifications: Audio notification requested, but sound file from notifyrc file was not found, aborting audio notification
Lock stolen
Open success.
kf.i18n: Trying to convert empty KLocalizedString to QString.
kf.i18n: Trying to convert empty KLocalizedString to QString.
zsh: segmentation fault (core dumped)  QT_QPA_PLATFORM=xcb parley

EXPECTED RESULT
Some window opens.

SOFTWARE/OS VERSIONS
Windows: -
macOS: -
Linux/KDE Plasma: Gentoo Linux with Plasma 5.27.4
(available in About System)
KDE Plasma Version: 5.27.4
KDE Frameworks Version: 5.104.0
Qt Version: 5.15.8

ADDITIONAL INFORMATION
Starting the program in GDB leads to this stack trace (typing `run`, reproduce the crash, and then `bt`)
```
#0  0x00007ffff611c56a in QByteArray::operator=(char const*) () from /usr/lib64/libQt5Core.so.5
#1  0x00007ffff766fcab in KLocalizedString::KLocalizedString(char const*, char const*, char const*, char const*, bool) ()
   from /usr/lib64/libKF5I18n.so.5
#2  0x000055555562ebc3 in BlockOptions::fillComboBox(KComboBox*) ()
#3  0x0000555555630b9c in BlockOptions::fillWidgets() ()
#4  0x00005555556315d8 in BlockOptions::BlockOptions(QWidget*) ()
#5  0x00005555555acd4b in ConfigurePracticeDialog::ConfigurePracticeDialog(KEduVocDocument*, QWidget*, QString const&, KConfigSkeleton*) ()
#6  0x00005555555ab240 in ParleyMainWindow::configurePractice() ()
#7  0x00007ffff62a76ff in void doActivate<false>(QObject*, int, void**) () from /usr/lib64/libQt5Core.so.5
#8  0x00007ffff6d5c7e2 in QAction::triggered(bool) () from /usr/lib64/libQt5Widgets.so.5
#9  0x00007ffff6d5f32b in QAction::activate(QAction::ActionEvent) () from /usr/lib64/libQt5Widgets.so.5
#10 0x00007ffff6ee3df2 in QMenuPrivate::activateCausedStack(QVector<QPointer<QWidget> > const&, QAction*, QAction::ActionEvent, bool) ()
   from /usr/lib64/libQt5Widgets.so.5
#11 0x00007ffff6eeb994 in QMenuPrivate::activateAction(QAction*, QAction::ActionEvent, bool) () from /usr/lib64/libQt5Widgets.so.5
#12 0x00007ffff6da4908 in QWidget::event(QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#13 0x00007ffff6d6307e in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#14 0x00007ffff6d6b5a2 in QApplication::notify(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#15 0x00007ffff6274e58 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/lib64/libQt5Core.so.5
#16 0x00007ffff6d6971e in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool, bool) ()
   from /usr/lib64/libQt5Widgets.so.5
#17 0x00007ffff6dbd995 in QWidgetWindow::handleMouseEvent(QMouseEvent*) () from /usr/lib64/libQt5Widgets.so.5
#18 0x00007ffff6dc08d0 in QWidgetWindow::event(QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#19 0x00007ffff6d6307e in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#20 0x00007ffff6274e58 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/lib64/libQt5Core.so.5
#21 0x00007ffff672b71d in QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent*) () from /usr/lib64/libQt5Gui.so.5
#22 0x00007ffff670b1fc in QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQt5Gui.so.5
#23 0x00007fffe771d5ba in xcbSourceDispatch(_GSource*, int (*)(void*), void*) () from /usr/lib64/libQt5XcbQpa.so.5
#24 0x00007fffebd1b559 in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#25 0x00007fffebd1b7e8 in g_main_context_iterate.constprop () from /usr/lib64/libglib-2.0.so.0
#26 0x00007fffebd1b87c in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#27 0x00007ffff62c4156 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQt5Core.so.5
#28 0x00007ffff62739aa in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib64/libQt5Core.so.5
#29 0x00007ffff627b77e in QCoreApplication::exec() () from /usr/lib64/libQt5Core.so.5
#30 0x00005555555a914a in main ()
```