Render None as empty string

[oliverroick]

Why I made this change

If you add or edit a party on the platform and leave non-required fields blank, number and date fields , which are blank, are displayed as None.

The render method of each attribute simply returns the value passed to the val parameter; for None values this results in "None" being displayed.

Description of the change

If the provided value is None return an empty string ('')

How someone else can test the change

Install this branch in the platform.

Create a project using this form. The form contains an integer field called number_children and a date field called dob.

Create a party, choose the party type "Individual" leave both number_children and dob blank. After saving you should check on the party detail page that no value is displayed for both fields.

When should this PR be merged

This is somewhat urgent to one partner so we need to get it through quickly.

Risks

None

Follow-up actions

• Release a new version of django-jsonattrs
• Update the platform requirements to that new version