Prevent accidental null dereference

[torben-hansen]

Issues:

P177717548

Description of changes:

Just make sure to prevent null-dereference.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.

Project coverage is 78.76%. Comparing base (2ab1f4d) to head (2592743).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
crypto/fipsmodule/cipher/cipher.c	76.92%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2046      +/-   ##
==========================================
- Coverage   78.78%   78.76%   -0.02%     
==========================================
  Files         598      598              
  Lines      103654   103676      +22     
  Branches    14736    14743       +7     
==========================================
- Hits        81661    81660       -1     
- Misses      21342    21364      +22     
- Partials      651      652       +1     

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[WillChilds-Klein]

minor nit: NULL param test coverage here?