Elasticsearch version: 2.1 - master

Description of the problem including expected versus actual behavior: Sending even an empty body (url localhost:9200/test/_settings -d '' or curl localhost:9200/test/_settings -d '{}') results in a (wrong) exception - mapper_parsing_exception

Steps to reproduce:

1. curl -X PUT localhost:9200/test
2. curl localhost:9200/test/_settings -d ''