Fixes process nodes for relation None

[BeArchiTek]

Fixes #331

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
infrahub_sdk/node.py	50.00%	0 Missing and 2 partials ⚠️

@@           Coverage Diff           @@
##           stable     #332   +/-   ##
=======================================
  Coverage   71.32%   71.32%           
=======================================
  Files          87       87           
  Lines        7871     7871           
  Branches     1517     1517           
=======================================
  Hits         5614     5614           
  Misses       1865     1865           
  Partials      392      392           

Flag	Coverage Δ
integration-tests	22.80% <50.00%> (ø)
python-3.10	45.45% <0.00%> (ø)
python-3.11	45.48% <0.00%> (ø)
python-3.12	45.45% <0.00%> (-0.03%)	⬇️
python-3.13	45.45% <0.00%> (-0.03%)	⬇️
python-3.9	44.35% <0.00%> (-0.03%)	⬇️
python-filler-3.12	24.66% <0.00%> (ø)

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Files with missing lines	Coverage Δ
infrahub_sdk/node.py	77.47% <50.00%> (ø)

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[ogenstad]

Would be nice with a test if possible :)

[ogenstad]

This is the only change that's required for the other ones relation = node_data["node"].get(rel_name) would already return None so we don't need a default value there.