crash when exporting a specific .sla file with a single text frame

[aoloe]

The SLA file below crashes the epub exporter when quering the character style

test2.sla

[aoloe]

the backtrace is:

#0  0x00000000011ed527 in CharStyle::displayName (this=0x2cb1410) at /home/ale/docs/src/scribus/scribus/styles/charstyle.cpp:172
#1  0x00007fffcccc0b23 in ScribusAPIDocumentItemFormatting::readAtPosition (this=0x7fffffffc7f0, item=0x2cafb20, position=0)
    at /home/ale/docs/src/scribus/scribus/plugins/export/epub/module/scribusAPIDocumentItemFormatting.cpp:32
#2  0x00007fffcccbbff3 in ScribusAPIDocumentItemFormatting::readAtPosition (this=0x7fffffffc7f0, position=0) at /home/ale/docs/src/scribus/scribus/plugins/export/epub/module/scribusAPIDocumentItemFormatting.h:49
#3  0x00007fffcccb8e01 in ScribusAPIDocumentItem::getTextDom (this=0x2632bc0, xhtmlDocument=...) at /home/ale/docs/src/scribus/scribus/plugins/export/epub/module/scribusAPIDocumentItem.cpp:77
#4  0x00007fffcccc1936 in EpubExportContent::fillEpub (this=0x2727080, epub=0x2ba1880, structure=0x2c9a3f0) at /home/ale/docs/src/scribus/scribus/plugins/export/epub/module/epubexportContent.cpp:51
#5  0x00007fffcccc53c8 in EpubExport::doExport (this=0x2de9de0) at /home/ale/docs/src/scribus/scribus/plugins/export/epub/epubexport.cpp:57
#6  0x00007fffccca0d5f in EpubExportPlugin::run (this=0x1ba8710, doc=0x2be25a0, target=...) at /home/ale/docs/src/scribus/scribus/plugins/export/epub/epubexportplugin.cpp:111
#7  0x0000000000733ff3 in ScActionPlugin::qt_static_metacall (_o=0x1ba8710, _c=QMetaObject::InvokeMetaMethod, _id=1, _a=0x7fffffffd4d0) at /home/ale/docs/src/scribus/build/scribus/moc_scplugin.cpp:163
#8  0x00007ffff768d91e in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#9  0x0000000000735781 in ScrAction::triggeredData (this=0x1ea9140, _t1=0x2be25a0) at /home/ale/docs/src/scribus/build/scribus/moc_scraction.cpp:266
#10 0x0000000000bec388 in ScrAction::triggeredToTriggeredData (this=0x1ea9140) at /home/ale/docs/src/scribus/scribus/scraction.cpp:121
#11 0x00000000007351df in ScrAction::qt_static_metacall (_o=0x1ea9140, _c=QMetaObject::InvokeMetaMethod, _id=11, _a=0x7fffffffd7e0) at /home/ale/docs/src/scribus/build/scribus/moc_scraction.cpp:117
#12 0x00007ffff768d91e in QMetaObject::activate(QObject*, int, int, void**) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#13 0x00007ffff6cac202 in QAction::triggered(bool) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#14 0x00007ffff6cae6e8 in QAction::activate(QAction::ActionEvent) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#15 0x00007ffff6e2063a in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#16 0x00007ffff6e24744 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#17 0x00007ffff6e26ce5 in QMenu::keyPressEvent(QKeyEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#18 0x00007ffff6cee31e in QWidget::event(QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#19 0x00007ffff6e28f1b in QMenu::event(QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#20 0x00007ffff6cb369c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#21 0x00007ffff6cb8bda in QApplication::notify(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#22 0x00007ffff765e9d5 in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#23 0x00007ffff6d0e003 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#24 0x00007ffff6cb369c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#25 0x00007ffff6cb8416 in QApplication::notify(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#26 0x00007ffff765e9d5 in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#27 0x00007ffff65532cb in QGuiApplicationPrivate::processKeyEvent(QWindowSystemInterfacePrivate::KeyEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
#28 0x00007ffff6557595 in QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePrivate::WindowSystemEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
#29 0x00007ffff653e328 in QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
#30 0x00007fffe434e8e0 in ?? () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so
#31 0x00007fffeda8de04 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#32 0x00007fffeda8e048 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#33 0x00007fffeda8e0ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#34 0x00007ffff76b56bc in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#35 0x00007ffff765c8eb in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#36 0x00007ffff7663f46 in QCoreApplication::exec() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#37 0x00000000011b2943 in mainApp (argc=1, argv=0x7fffffffe448) at /home/ale/docs/src/scribus/scribus/main_nix.cpp:86
#38 0x00000000011b28d3 in main (argc=1, argv=0x7fffffffe448) at /home/ale/docs/src/scribus/scribus/main_nix.cpp:54