Check that the request don't get deleted in a slot

Deleting sender() in a slot isn't allowed, really.
Produce an assert for now to help the existing users fix their code.

Change-Id: I784ec6f7bc0116b4bf5be8da086dae9492bf3aea
Reviewed-by: Michael Krasnyk <michael.krasnyk@gmail.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Notify the request destruction from Q*AbstractRequest dtor

...rather than from subclass'es dtor.
This brings us closer to what QObject does, disallowing fancy
manipulations on a partially destroyed request.

Change-Id: Ifaa31e4fbf7bde552b4ca62676ae25c5b8dc8ac5
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
QtOrganizer: fix SortOrder initialization

Method QDeclarativeOrganizerItemSortOrder::sortOrder()
can be called before a componentComplete() call
that leads to an uninitialized sort order private data.

Change-Id: I4c16642cc30563a05a43e8fcd60aa4e7e5dc7f1b
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Require the request be non-null

Handlers shouln't silently ignore a null requests; if the request
is null, then something went wrong and must be fixed.

Change-Id: Ic0691fd87e0c8b2e3081e539d75db247b6d4ae78
Reviewed-by: Michael Krasnyk <michael.krasnyk@gmail.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Matthew Vogt <matthew.vogt@qinetic.com.au>
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>