The Linux backtrace is as follows:

(gdb) run
[...]
Thread 1 "sigil" received signal SIGSEGV, Segmentation fault.
0x00007ffff70a46f0 in QWidget::mapToParent(QPoint const&) const ()
   from /usr/lib/libQt5Widgets.so.5
Thread 1 "sigil" received signal SIGSEGV, Segmentation fault.
0x00007ffff70a46f0 in QWidget::mapToParent(QPoint const&) const ()
   from /usr/lib/libQt5Widgets.so.5

(gdb) backtrace
#0  0x00007ffff70a46f0 in QWidget::mapToParent(QPoint const&) const ()
    at /usr/lib/libQt5Widgets.so.5
#1  0x00007ffff70a4754 in QWidget::mapTo(QWidget const*, QPoint const&) const
    () at /usr/lib/libQt5Widgets.so.5
#2  0x00007ffff708959b in  () at /usr/lib/libQt5Widgets.so.5
#3  0x00007ffff708b1fb in  () at /usr/lib/libQt5Widgets.so.5
#4  0x00007ffff708c3a5 in  () at /usr/lib/libQt5Widgets.so.5
#5  0x00007ffff708cba9 in  () at /usr/lib/libQt5Widgets.so.5
#6  0x00007ffff70a4b47 in QWidgetPrivate::syncBackingStore() ()
    at /usr/lib/libQt5Widgets.so.5
#7  0x00007ffff70bdeb7 in QWidget::event(QEvent*) ()
    at /usr/lib/libQt5Widgets.so.5
#8  0x00007ffff707a485 in QApplicationPrivate::notify_helper(QObject*, QEvent*)
    () at /usr/lib/libQt5Widgets.so.5
#9  0x00007ffff70839b1 in QApplication::notify(QObject*, QEvent*) ()
    at /usr/lib/libQt5Widgets.so.5
#10 0x00007fffef2d7782 in QCoreApplication::notifyInternal2(QObject*, QEvent*)
    () at /usr/lib/libQt5Core.so.5
#11 0x00007fffef2da459 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /usr/lib/libQt5Core.so.5
#12 0x00007fffef32fc64 in  () at /usr/lib/libQt5Core.so.5
#13 0x00007fffeb20690f in g_main_context_dispatch ()
    at /usr/lib/libglib-2.0.so.0
#14 0x00007fffeb208869 in  () at /usr/lib/libglib-2.0.so.0
#15 0x00007fffeb2088ae in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0
#16 0x00007fffef32f263 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#17 0x00007fffef2d63ac in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) ()
    at /usr/lib/libQt5Core.so.5
#18 0x00007fffef2de056 in QCoreApplication::exec() () at /usr/lib/libQt5Core.so.5
#19 0x0000555555725fcf in main(int, char**) (argc=1, argv=0x7fffffffe7a8)
    at /home/pc300/Sigil/src/main.cpp:405