zlib: add CHECK to validate fast path input

[mcollina]

Add missing CHECK in FastCRC32 to match the slow path.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 88.53%. Comparing base (4f24aff) to head (c2aaa42).
⚠️ Report is 58 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_zlib.cc	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #61175   +/-   ##
=======================================
  Coverage   88.53%   88.53%           
=======================================
  Files         703      703           
  Lines      208546   208599   +53     
  Branches    40217    40231   +14     
=======================================
+ Hits       184634   184690   +56     
+ Misses      15926    15911   -15     
- Partials     7986     7998   +12     

Files with missing lines	Coverage Δ
src/node_zlib.cc	77.79% <0.00%> (-0.08%)	⬇️

... and 60 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/70605/