When key is None, give up if _DB_get_type() returns -1 as well.

Modules/_bsddb.c

@@ -350,6 +350,8 @@ make_key_dbt(DBObject* self, PyObject* keyobj, DBT* key, int* pflags)
     CLEAR_DBT(*key);
     if (keyobj == Py_None) {  /* TODO: is None really okay for keys? */
         type = _DB_get_type(self);
+        if (type == -1)
+            return 0;
         if (type == DB_RECNO || type == DB_QUEUE) {
             PyErr_SetString(
                 PyExc_TypeError,