Previously, QStandardItem::operator<() returned true when both
items had invalid data. With MSVC in debug mode (checked
iterators/STL), this triggered an assert in
tst_QStandardItem::sortChildren() since that verifies
that !(b < a) when a < b:
Debug Assertion Failed!
Line: 3006
Expression: invalid operator<
Introduce a stable sort order for invalid items such that
other items are always less than invalid items and comparing
invalid items returns false (indicating equivalence).
Change-Id: Ica0f0d9f001c86973b1941dbcc1faf282e4c47df
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
56d62345ad