twilio/flask-restful — pull request #328 by Ch00k (2014-11-12 19:58:41+00:00)
Title: Allow for returning an empty dict if Nested object is None

Flask-RESTful only allows returning null if the object that is marshaled with Nested is None. This change adds a kwarg to allow returning an empty object instead (which seems like a better idea for the JSON object).
Example:
```
{
"movie": {
"id": 997,
"imdb_data": {
"id": 816692,
"rating": "9.0",
"title": "Interstellar"
},
"show_end": 1416952800,
"show_start": 1415224800,
"title": "Interstellar",
"url": "http://planeta-kino.com.ua/lvov/movies/interstellar/"
}
}
```
If there is no IMDB data for a movie then return an empty object:
```
{
"movie": {
"id": 1315,
"imdb_data": {},
"show_end": null,
"show_start": 1417644000,
"title": "Trash",
"url": "http://planeta-kino.com.ua/lvov/movies/trash/"
}
}
```
Inspired by this SA question: http://stackoverflow.com/q/26867357/695332