PyQt4 backend delete the widow in C++ but not in Python

This is the BUG:

If you close the window clicking on the right cross to close the
window the window closes properly. If you then try to create a new
widow (with the same index) you hit a RunTimeError.


The window should be created normally.

It seems that the pyQt4 backend doesn't delete the window in the
python world but it does delete it in the C++.

Any ideas hot to fix it?