feat: fix g2 bug in addNamedDomainMatchingFunc()

[zhuying1999]

After comparing the Go version, I felt that the commented out code was the main cause of NPE.

Fix: #362

[casbin-bot]

@tangyang9464 @imp2002 please review

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[codecov-commenter]

Codecov Report

Merging #363 (6de6ec6) into master (7297b01) will decrease coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #363      +/-   ##
==========================================
- Coverage   69.50%   69.46%   -0.05%     
==========================================
  Files          49       49              
  Lines        2243     2240       -3     
  Branches      399      398       -1     
==========================================
- Hits         1559     1556       -3     
- Misses        573      574       +1     
+ Partials      111      110       -1     

Files	Coverage Δ
...ain/java/org/casbin/jcasbin/main/CoreEnforcer.java	77.39% <ø> (-0.23%)	⬇️

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[github-actions]

🎉 This PR is included in version 1.41.0 🎉

The release is available on:

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• v1.41.0

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