No zeros (0) displayed in the swagger-ui documentation examples, if provided as a number

[Nantero1]

version: flask-restplus=0.13.0
A code sample to reproduce the issue:
take this example line

flask-restplus/examples/todomvc.py

Line 14 in 1fe65dd

'id': fields.Integer(readonly=True, description='The task unique identifier'),

and replace it by
'id': fields.Integer(description='The task unique identifier', example=0),

You will notice, that 0 will be ignored in the swagger documentation. Passing the string "0" as a value works fine. Passing any other number not as a string works fine as well. Empty lists ([]) don't work either.

Why this happens

This line evaluates wrongly, if the passed variable "example" is set to 0.

flask-restplus/flask_restplus/fields.py

Line 123 in 1fe65dd

self.example = example or self.__schema_example__

Swagger documentation is not created correctly, if 0 as an integer or 0.0 as a float example values in the api.model definition are provided.

Screenshot from created swagger documentation:

Debugger screenshot, self.example != example

Update: An empty list as an example "[]" for list fields evaluates wrongly too.

Partly working workaround

Always use a string, double quoted zero ("0" ) as an example value. But this breaks type safety. field example value will have the wrong type (string).

This workaround does not work for empty list examples example=[]