[ISSUE #8909] Move nullcheck ahead

[jjastan]

Which Issue(s) This PR Fixes

Fixes #8909

Brief Description

Move nullcheck ahead

How Did You Test This Change

No test.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 47.52%. Comparing base (321670a) to head (9d3ed5d).
Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
...rocketmq/common/config/AbstractRocksDBStorage.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #8910      +/-   ##
=============================================
- Coverage      47.54%   47.52%   -0.03%     
- Complexity     11729    11735       +6     
=============================================
  Files           1304     1304              
  Lines          91058    91058              
  Branches       11678    11677       -1     
=============================================
- Hits           43295    43274      -21     
- Misses         42415    42435      +20     
- Partials        5348     5349       +1     

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