Exception when serializing a JSONObject with null values

[mpoindexter]

When attempting to serialize a JSONObject with a null value the following exception is thrown:

java.util.NoSuchElementException: JSONObject["xxxx"] not found.
at org.json.JSONObject.get(JSONObject.java:220)
at com.fasterxml.jackson.datatype.jsonorg.JSONObjectSerializer.serializeContents(JSONObjectSerializer.java:57)
at com.fasterxml.jackson.datatype.jsonorg.JSONObjectSerializer.serialize(JSONObjectSerializer.java:28)
at com.fasterxml.jackson.datatype.jsonorg.JSONObjectSerializer.serialize(JSONObjectSerializer.java:14)

It seems like the following code in JSONObjectSerializer

        try {
            ob = value.get(key);
        } catch (JSONException e) {
            throw new JsonGenerationException(e);
        }
        if (ob == null || ob == JSONObject.NULL) {
            if (provider.isEnabled(SerializationConfig.Feature.WRITE_NULL_MAP_VALUES)) {
                jgen.writeNullField(key);
            }
            continue;
        }

should instead be:

        try {
            ob = value.opt(key);
        } catch (JSONException e) {
            throw new JsonGenerationException(e);
        }
        if (ob == null || ob == JSONObject.NULL) {
            if (provider.isEnabled(SerializationConfig.Feature.WRITE_NULL_MAP_VALUES)) {
                jgen.writeNullField(key);
            }
            continue;
        }

[cowtowncoder]

Ok. Fix is in, although I wasn't able to reproduce the original issue; but change makes sense regardless.