We don't load and save pointers usually because the pointer value cannot
be guaranteed to remain across program invocations. However, nullptr is
an exception: a null pointer is always a null pointer.
We don't actually have to read or write anything: there's only one value
possible for a std::nullptr_t and it is nullptr.
[ChangeLog][Important Behavior Changes] A QVariant containing a
std::nullptr_t is now streamable to/from QDataStream.
Task-number: QTBUG-59391
Change-Id: Iae839f6a131a4f0784bffffd14aa374f6475d283
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
99fc96fd37