[PYG-350] Aggregate when filter return empty

[doctrino]

Description

If you add a filter to your aggregates which filters out all results the value will not be in the response:

Checklist:

• Tests added/updated.
• Documentation updated. Documentation is generated from docstrings - these must be updated according to your change.
  If a new method has been added it should be referenced in cognite.rst in order to generate docs based on its docstring.
• Changelog updated in CHANGELOG.md.
• Version bumped. If triggering a new release is desired, bump the version number in _version.py and pyproject.toml per semantic versioning.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.37%. Comparing base (11cf2b4) to head (11a03f7).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2124      +/-   ##
==========================================
- Coverage   90.38%   90.37%   -0.01%     
==========================================
  Files         152      152              
  Lines       23127    23125       -2     
==========================================
- Hits        20903    20900       -3     
- Misses       2224     2225       +1     

Files with missing lines	Coverage Δ
cognite/client/_version.py	100.00% <100.00%> (ø)
cognite/client/data_classes/aggregations.py	89.84% <100.00%> (-0.08%)	⬇️

... and 1 file with indirect coverage changes

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[erlendvollset]

LGTM

[rbtcollins]

This change isn't described by your PR description. Is it accidental, or deliberately but undocumented?

[rbtcollins]

one small question