Fixes #3379 - added check for no fields in point

[jhorwit2]

#3379

Before, which caused panic

curl -i -XPOST 'http://localhost:8086/write?db=mydb' --data-binary 'cpu_load_short,host=server01,region=us-west'
curl: (52) Empty reply from server

after:

curl -i -XPOST 'http://localhost:8086/write?db=mydb' --data-binary 'cpu_load_short,host=server01,region=us-west'
HTTP/1.1 400 Bad Request
Request-Id: aecd185d-2f44-11e5-8001-000000000000
X-Influxdb-Version: 0.9
Date: Tue, 21 Jul 2015 01:06:14 GMT
Content-Length: 78
Content-Type: text/plain; charset=utf-8

unable to parse 'cpu_load_short,host=server01,region=us-west': missing fields

[otoolep]

@jwilder

[jhorwit2]

Another possible spot for this error is in the first if conditional in the for loop at the top of the function. That might be cleaner as there is already an if check on buf size.

[jhorwit2]

Actually it's probably best where it's at just in case someone adds a premature break to that loop in the future.

[jwilder]

👍 Thanks @jhorwit2