Fix reference counting

src/js2python.cpp

@@ -70,6 +70,7 @@ PyObject *jsToPythonKwargs(val kwargs) {
     PyObject *k = jsToPython(keys[i]);
     PyObject *v = jsToPython(kwargs[keys[i]]);
     if (PyDict_SetItem(pykwargs, k, v)) {
+      Py_DECREF(pykwargs);
       return NULL;
     }
     Py_DECREF(k);