QTextEdit crashes in some weird circumstances

1  QVector<QScriptLine>::operator[]                                                                                                                          qvector.h                  438  0x7ffff731f365 
2  QTextLine::height                                                                                                                                         qtextlayout.cpp            1491 0x7ffff7315fd9 
3  QTextDocumentLayoutPrivate::layoutFlow                                                                                                                    qtextdocumentlayout.cpp    2497 0x7ffff735e184 
4  QTextDocumentLayoutPrivate::layoutFrame                                                                                                                   qtextdocumentlayout.cpp    2205 0x7ffff7361a5d 
5  QTextDocumentLayoutPrivate::layoutFrame                                                                                                                   qtextdocumentlayout.cpp    2094 0x7ffff7361f93 
6  QTextDocumentLayout::doLayout                                                                                                                             qtextdocumentlayout.cpp    3001 0x7ffff7362097 
7  QTextDocumentLayout::documentChanged                                                                                                                      qtextdocumentlayout.cpp    2964 0x7ffff7362f49 
8  QTextDocumentPrivate::finishEdit                                                                                                                          qtextdocument_p.cpp        1220 0x7ffff733fe2e 
9  QTextDocumentPrivate::endEditBlock                                                                                                                        qtextdocument_p.cpp        1201 0x7ffff73402a9 
10 QTextCursor::endEditBlock                                                                                                                                 qtextcursor.cpp            2510 0x7ffff736aa42 
11 MainWindow::highlight                                                                                                                                     mainwindow.cpp             53   0x403a05       
12 QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, void (MainWindow:: *)()>::call(void (MainWindow:: *)(), MainWindow *, void * *) qobjectdefs_impl.h         136  0x404e5e       
13 QtPrivate::FunctionPointer<void (MainWindow:: *)()>::call<QtPrivate::List<>, void>(void (MainWindow:: *)(), MainWindow *, void * *)                       qobjectdefs_impl.h         169  0x404df0       
14 QtPrivate::QSlotObject<void (MainWindow:: *)(), QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void * *, bool *)            qobject_impl.h             120  0x404d5a       
15 QtPrivate::QSlotObjectBase::call                                                                                                                          qobject_impl.h             101  0x7ffff6e89893 
16 QMetaObject::activate                                                                                                                                     qobject.cpp                3749 0x7ffff6e89893 
17 QMetaObject::activate                                                                                                                                     qobject.cpp                3628 0x7ffff6e89df5 
18 QAbstractButton::clicked                                                                                                                                  moc_qabstractbutton.cpp    309  0x7ffff7a43266 
19 QAbstractButtonPrivate::emitClicked                                                                                                                       qabstractbutton.cpp        410  0x7ffff7a43474 
20 QAbstractButtonPrivate::click                                                                                                                             qabstractbutton.cpp        403  0x7ffff7a44d3d 
21 QAbstractButton::mouseReleaseEvent                                                                                                                        qabstractbutton.cpp        1006 0x7ffff7a44fe0 
22 QWidget::event                                                                                                                                            qwidget.cpp                8796 0x7ffff788d796 
23 QAbstractButton::event                                                                                                                                    qabstractbutton.cpp        964  0x7ffff7a462de 
24 QPushButton::event                                                                                                                                        qpushbutton.cpp            689  0x7ffff7a50aff 
25 QApplicationPrivate::notify_helper                                                                                                                        qapplication.cpp           3717 0x7ffff78427a3 
26 QApplication::notify                                                                                                                                      qapplication.cpp           3193 0x7ffff784aa4b 
27 QCoreApplication::notifyInternal2                                                                                                                         qcoreapplication.cpp       1018 0x7ffff6e5a1f8 
28 QCoreApplication::sendSpontaneousEvent                                                                                                                    qcoreapplication.h         236  0x7ffff78497f1 
29 QApplicationPrivate::sendMouseEvent                                                                                                                       qapplication.cpp           2697 0x7ffff78497f1 
30 QWidgetWindow::handleMouseEvent                                                                                                                           qwidgetwindow.cpp          618  0x7ffff78ab054 
31 QWidgetWindow::event                                                                                                                                      qwidgetwindow.cpp          239  0x7ffff78ad327 
32 QApplicationPrivate::notify_helper                                                                                                                        qapplication.cpp           3717 0x7ffff78427a3 
33 QApplication::notify                                                                                                                                      qapplication.cpp           3089 0x7ffff784a54e 
34 QCoreApplication::notifyInternal2                                                                                                                         qcoreapplication.cpp       1018 0x7ffff6e5a1f8 
35 QCoreApplication::sendSpontaneousEvent                                                                                                                    qcoreapplication.h         236  0x7ffff72356a6 
36 QGuiApplicationPrivate::processMouseEvent                                                                                                                 qguiapplication.cpp        1936 0x7ffff72356a6 
37 QGuiApplicationPrivate::processWindowSystemEvent                                                                                                          qguiapplication.cpp        1720 0x7ffff7236fa8 
38 QWindowSystemInterface::sendWindowSystemEvents                                                                                                            qwindowsysteminterface.cpp 938  0x7ffff720dc5b 
39 QUnixEventDispatcherQPA::processEvents                                                                                                                    qunixeventdispatcher.cpp   69   0x7ffff7f57560 
40 QEventLoop::processEvents                                                                                                                                 qeventloop.cpp             134  0x7ffff6e58053 
41 QEventLoop::exec                                                                                                                                          qeventloop.cpp             212  0x7ffff6e58499 
42 QCoreApplication::exec                                                                                                                                    qcoreapplication.cpp       1291 0x7ffff6e61ff2 
43 QGuiApplication::exec                                                                                                                                     qguiapplication.cpp        1666 0x7ffff722cca4 
44 QApplication::exec                                                                                                                                        qapplication.cpp           2905 0x7ffff7842635 
45 main                                                                                                                                                      main.cpp                   10   0x403561