Corrected empty lists being returned instead of none for uniqued lists

[SteveMcGrath]

Description

Sync API datamodels use a lambda-based serializer for unique lists that created empty lists in the output models when
they are unsupported upstream. This simple fix corrects that.

Type of change

Please delete options that are not relevant.

• 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)
• This change requires a documentation update

How Has This Been Tested?

❯ ptpython
>>> test = lambda v: list(set(v)) if v and len(v) > 0 else None
>>> test([1, 2, 3, 3, 4, 5, 6, 7])
[1, 2, 3, 4, 5, 6, 7]
>>> test([])
>>>

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[github-actions]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
8478	8101	96%	0%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
tenable/io/sync/models/common.py	97%	🟢
tenable/version.py	100%	🟢
TOTAL	99%	🟢

updated for commit: b288027 by action🐍