Fix reference counting problem, triggered by subclass-able class not being subclassed, which is detected only by a debug Python build.
Fix reference counting problem, triggered by subclass-able class not being subclassed, which is detected only by a debug Python build.

caramucho/pybindgen,cawka/pybindgen,cawka/pybindgen,caramucho/pybindgen,caramucho/pybindgen,caramucho/pybindgen,cawka/pybindgen,cawka/pybindgen