[#378] Prevent crash if reviewItem has zaak = null

[SilviaAmAm]

Fixes #378

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 8.62069% with 53 lines in your changes missing coverage. Please review.

Project coverage is 76.52%. Comparing base (1899acd) to head (758c0f3).

Files with missing lines	Patch %	Lines
...ion/tests/e2e/features/test_feature_list_review.py	9.09%	20 Missing ⚠️
...s/e2e/features/test_feature_list_process_review.py	9.52%	19 Missing ⚠️
...ructionlist/detail/DestructionListDetail.loader.ts	0.00%	2 Missing and 4 partials ⚠️
frontend/src/fixtures/reviewItem.ts	0.00%	4 Missing ⚠️
...ructionlist/review/DestructionListReview.loader.ts	0.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #379      +/-   ##
==========================================
- Coverage   76.94%   76.52%   -0.43%     
==========================================
  Files         240      240              
  Lines        7504     7552      +48     
  Branches      158      160       +2     
==========================================
+ Hits         5774     5779       +5     
- Misses       1583     1624      +41     
- Partials      147      149       +2     

Flag	Coverage Δ
	76.52% <8.62%> (-0.43%)	⬇️

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