json:serialize returns invalid json

The json:serialize function returns syntactically incorrect json.

For example, the existing test query serialize_json_18.xq fails because it's missing an ending curly '}' as follows:

import module namespace json = "http://www.zorba-xquery.com/modules/converters/json";
import schema namespace html-options="http://www.zorba-xquery.com/modules/converters/json-options";

declare variable $tmp := <json type="object"><pair name="phoneNumbers" type="array"><item type="string">212 732-1234</item><item type="string">646 123-4567</item></pair><pair name="firstName" type="string">John</pair><pair name="lastName" type="string">Smith</pair><pair name="address" type="object"><pair name="postalCode" type="number">10021</pair><pair name="city" type="string">New York</pair><pair name="streetAddress" type="string">21 2nd Street</pair><pair name="state" type="string">NY</pair></pair></json>;

json:serialize($tmp)

Actual: <<root>{"phoneNumbers": ["212 732-1234", "646 123-4567"], "firstName": "John", "lastName": "Smith", "address": {"postalCode": 10021, "city": "New York", "streetAddress": "21 2nd Street", "state": "NY"}</root>>

Expected: <<root>{"phoneNumbers": ["212 732-1234", "646 123-4567"], "firstName": "John", "lastName": "Smith", "address": {"postalCode": 10021, "city": "New York", "streetAddress": "21 2nd Street", "state": "NY"}}>