different segfault with lastest master

[Linus Torvalds]

Hmm. I'm not sure how to reproduce this, because I was just moving
around between the dives, checking out how the globe moved, and
occasionally pressing the dive site quick-edit button.

And suddenly I get

*** Error in `/home/torvalds/src/install-root/bin/subsurface':
malloc(): memory corruption (fast): 0x0000000005a9f01f ***

with the call stack being

#0  0x00007fffefa67a98 in raise () at /lib64/libc.so.6
#1  0x00007fffefa6972a in abort () at /lib64/libc.so.6
#2  0x00007fffefaaaea2 in  () at /lib64/libc.so.6
#3  0x00007fffefab3ef8 in _int_malloc () at /lib64/libc.so.6
#4  0x00007fffefab6b5e in malloc () at /lib64/libc.so.6
#5  0x00007ffff042d453 in QArrayData::allocate(unsigned long, unsigned
long, unsigned long, QFlags<QArrayData::AllocationOption>) () at
/lib64/libQt5Core.so.5
#6  0x00007ffff04b9b1f in QString::QString(int, QChar) () at
/lib64/libQt5Core.so.5
#7  0x00007ffff04978f7 in QLocalePrivate::dateTimeToString(QString
const&, QDateTime const&, QDate const&, QTime const&, QLocale const*)
const () at /lib64/libQt5Core.so.5
#8  0x00007ffff049867e in QLocale::toString(QDateTime const&, QString
const&) const () at /lib64/libQt5Core.so.5
#9  0x00007ffff1692e64 in QDateTimeEdit::textFromDateTime(QDateTime
const&) const () at /lib64/libQt5Widgets.so.5
#10 0x00007ffff1692d63 in QDateTimeEditPrivate::textFromValue(QVariant
const&) const () at /lib64/libQt5Widgets.so.5
#11 0x00007ffff169341b in QDateTimeEditPrivate::updateEdit() () at
/lib64/libQt5Widgets.so.5
#12 0x00007ffff167815c in QAbstractSpinBoxPrivate::setValue(QVariant
const&, EmitPolicy, bool) ()
    at /lib64/libQt5Widgets.so.5
#13 0x00007ffff1693668 in QDateTimeEdit::setTime(QTime const&) () at
/lib64/libQt5Widgets.so.5
#14 0x00000000005e3f19 in MainTab::updateDiveInfo(bool)
(this=0xeed8a0, clear=false)
    at /home/torvalds/src/subsurface/qt-ui/maintab.cpp:539
#15 0x00000000004fafd0 in MainWindow::current_dive_changed(int)
(this=0xdadfb0, divenr=469)
    at /home/torvalds/src/subsurface/qt-ui/mainwindow.cpp:268
...

which doesn't look very interesting. The corruption probably happened
at some earlier point.

I tried to run it under valgrind in case that shows anything more
interesting, but that actually crashed very quickly in WTFCrash with
address 0xbbadbeef, which seems to be some WebKit issue with valgrind.
Googling valgrind and WTFCrash and "0xbbadbeef" implies I'm not the
only one, but it makes valgrind not give anything useful for this.

Sorry for useless bug report. I don't know what else to try.

              Linus