Get "No data received" error when connecting a non-localhost mongod

[feifangit]

Sorry, the title is incorrect, I can updated the issue body, but can not update the title.
the problem is:
with the combination field=filename type=string, everything works fine.
but the combination field=_id type=string gets the error No data received

---

### nginx-gridfs version 0.8 ### Nginx version

nginx version: nginx/1.4.4
built by gcc 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) 
configure arguments: --add-module=/home/ubuntu/nginx-gridfs/ --with-cc-opt=-Wno-error

Nginx config

location /gridfsfn/{
   gridfs test1 type=string field=_id;
}

MongoDB content

> db.fs.files.find({},{_id:1})
{ "_id" : "1m" }
{ "_id" : "1k" }
{ "_id" : "100k" }
{ "_id" : "100m" }

HTTP request

..... /gridfsfn/1k

chrome return

Unable to load the webpage because the server sent no data.
Error code: ERR_EMPTY_RESPONSE

wget return

--2013-12-22 00:44:13--  http://localhost/gridfsfn/1k
Resolving localhost (localhost)... 127.0.0.1
Connecting to localhost (localhost)|127.0.0.1|:80... connected.
HTTP request sent, awaiting response... No data received.
Retrying.

--2013-12-22 00:44:14--  (try: 2)  http://localhost/gridfsfn/1k
Connecting to localhost (localhost)|127.0.0.1|:80... connected.
HTTP request sent, awaiting response... No data received.
Retrying.

....

Nginx log

2013/12/22 00:51:09 [alert] 1178#0: worker process 20484 exited on signal 11 (core dumped)