plugins/python/python_plugin_common.c: release py_args in close

even if the arguments are not used (eg. when there is no "close" call
in the plugin).

It was not really a memleak, because interpreter is deinitialized anyway,
which frees the object.

plugins/python/python_plugin_common.c

@@ -510,10 +510,13 @@ python_plugin_close(struct PluginContext *plugin_ctx, const char *callback_name,
             sudo_debug_printf(SUDO_DEBUG_INFO, "Python plugin function 'close' is skipped (not present)\n");
         } else {
             PyObject *py_result = python_plugin_api_call(plugin_ctx, callback_name, py_args);
+            py_args = NULL;  // api call already freed it
             Py_XDECREF(py_result);
         }
     }
 
+    Py_CLEAR(py_args);
+
     if (PyErr_Occurred()) {
         py_log_last_error(NULL);
     }