Link to issue number:

None

Summary of the issue:

The description fields in the manifest are optional, and default to None.
This is not handled by the add-on models correctly, which expect the description field to always be a string

Description of user facing changes

Add-ons without descriptions can be correctly viewed in the add-on store

Description of development approach

return an empty string if there is no description for the add-on.

Testing strategy:

Manual testing

Known issues with pull request:

None

Change log entries:

N/A

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English
• Security precautions taken.