fix bug of segmentation fault when item is not a string
fix bug of segmentation fault when item is not a string

swoole/swoole-src,LinkedDestiny/swoole-src,LinkedDestiny/swoole-src,tutanhamon/swoole-src,LinkedDestiny/swoole-src,tutanhamon/swoole-src,swoole/swoole-src,swoole/swoole-src,swoole/swoole-src,LinkedDestiny/swoole-src,tutanhamon/swoole-src,tutanhamon/swoole-src,tutanhamon/swoole-src,swoole/swoole-src,LinkedDestiny/swoole-src,swoole/swoole-src,swoole/swoole-src,tutanhamon/swoole-src,LinkedDestiny/swoole-src,tutanhamon/swoole-src,LinkedDestiny/swoole-src