The external table file path cache may out of date, which will cause orc reader to visit non-exist files. In this case, orc file reader is nullptr. This pr is to check the reader before using it to avoid core dump of visiting nullptr.
The external table file path cache may out of date, which will cause orc reader to visit non-exist files. In this case, orc file reader is nullptr. This pr is to check the reader before using it to avoid core dump of visiting nullptr.