The QtConcurrent::RunFunctionTask class keeps a variable to store the
result of QtConcurrent::run when it becomes available, so that it can be
reported afterwards. This requires the result type to be
default-constructible. However there's no need in storing the result, it
can be reported immediately after it becomes available.
Pick-to: 6.1 6.2
Fixes: QTBUG-95214
Change-Id: I95f3dbff0ab41eaa81b104a8834b37d10a0d193a
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>