Fix the null timer bug.
Fix the null timer bug.

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