Fix ItemHydraTest after removing boost::shared_ptr

The particalar check was to ensure that we don't try to cast between
two different shared pointers when the value is null. Originally Gerd
was boost::shared_ptr while Rudi was std::shared_ptr. After porting
wawy from boost I changed both to std::shared_ptr, so the check was
trying to cast from std::shared_ptr to std::shared_ptr. That is a
no-op and thus the operation was successful. Now I changed the check
to try cast between std::shared_ptr and QSharedPointer, which fails
as expected.