Include false and empty fields in the "license_reference"

[pombredanne]

Following up from #3154 (review)

I think we should include all the attributes that are empty in the license references. For instance in https://github.com/nexB/scancode-toolkit/blob/f1cc917e002d4269869ffefa47acb1bdfb3d2d56/src/licensedcode/models.py#L393 we do not report these.