Creation of a view with only the map fails

[mazzal1]

Code:
views.put(VIEW_BY_STATE_NAME, new CouchDesignDocument.View("function(doc) {" + "if(doc.state) {" + "emit(doc.state, doc);" + "}" + "}"));
In the code, only the map is set.

Error log:
request failed with code 400 {"error":"invalid_design_doc","reason":"views.byState.reduce field must have string type"}

Hint: probably the reduce is sent as "null" instead of being undefined.