[Regression] C++ object is not garbage-collected if a connection has been made from a script

The attached program behaves differently with Qt 4.6 than with 4.5. With 4.5, when the reference to the script object is removed (by setting it to null), the C++ object is deleted in the subsequent garbage collection. With 4.6, the object is not deleted.
The only workaround is to explicitly disconnect from the signal in the script before setting the reference to null.