fix: Set sig to Array when empty

[ChevronTango]

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Fixes #531

Release Notes: missing signatures are now empty arrays rather than null

Types of changes:

• [ x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected). Please ensure that your PR title is a Conventional Commit breaking change (with a !, as in feat!: change foo).

Description of the changes being introduced by the pull request:

The init command and others now returns an empty array rather than a null for the signatures field.

Please verify and check that the pull request fulfills the following requirements:

• [ ] Tests have been added for the bug fix or new feature
• [ ] Docs have been added for the bug fix or new feature

[ChevronTango]

@rdimitrov is there anything more I can do to help get this merged?