Core documents for a License shouldn't display a category

Overview:
Core documents cannot have a category, so when they are displayed in the UI no category property should display. Currently the category displays as blank

NB This behaviour is for Core documents on licenses only. The behaviour for supplementary documents on Licenses (and agreements) is correct

Steps to Reproduce:

1. Create a License and add a Core doc
2. View the license

Expected Results:
Core document displays without a category property

Actual Results:
Core document displays with a blank category property