fix add null-check to avoid NPE for issue #1882

[yanxutao89]

What this PR does / why we need it?

fix add null-check to avoid NPE for issue #1882

Summary of your change

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.

[codecov-commenter]

Codecov Report

Patch coverage: 86.48% and project coverage change: -0.01% ⚠️

Comparison is base (8940c14) 73.26% compared to head (8490c6f) 73.26%.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1892      +/-   ##
============================================
- Coverage     73.26%   73.26%   -0.01%     
+ Complexity    21546    21545       -1     
============================================
  Files           646      646              
  Lines         87407    87412       +5     
  Branches      19088    19090       +2     
============================================
- Hits          64040    64039       -1     
- Misses        15458    15461       +3     
- Partials       7909     7912       +3     

Files Changed	Coverage Δ
...libaba/fastjson2/reader/ObjectReaderException.java	79.31% <33.33%> (-0.61%)	⬇️
...on2/reader/ObjectReaderNoneDefaultConstructor.java	73.64% <89.47%> (-0.27%)	⬇️
.../alibaba/fastjson2/reader/ObjectReaderCreator.java	80.13% <93.33%> (-0.07%)	⬇️

... and 1 file with indirect coverage changes

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