Fix memory leaks in Shiboken

#include <Python.h>

#include <QCoreApplication>
#include <QDebug>

using namespace std;

void test()
{
    qWarning() << "init";
    Py_Initialize();

    {
        auto mainModule = PyImport_ImportModule("__main__");
        auto globalDict = PyModule_GetDict(mainModule);

        auto compiled = Py_CompileString("from PySide2 import QtCore\n", "test.py", Py_file_input);
        qWarning() << compiled;

        auto ret = PyEval_EvalCode(compiled, globalDict, globalDict);
        qWarning() << ret;

        Py_XDECREF(ret);
        Py_XDECREF(compiled);
        Py_XDECREF(mainModule);
    }

    Py_Finalize();
    qWarning() << "deinit";
}

int main(int argc, char** argv)
{
    QCoreApplication app(argc, argv);
    test();
    return 0;
}