[ISSUE #8895] Fix NPE when broker shutdown and optimize the log

[qianye1001]

Which Issue(s) This PR Fixes

Fixes #8895

Brief Description

How Did You Test This Change?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 47.92%. Comparing base (b30afe8) to head (36bf4d6).

Files with missing lines	Patch %	Lines
...rocketmq/common/config/AbstractRocksDBStorage.java	0.00%	1 Missing ⚠️
...org/apache/rocketmq/store/DefaultMessageStore.java	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #9094      +/-   ##
=============================================
- Coverage      47.93%   47.92%   -0.01%     
  Complexity     12049    12049              
=============================================
  Files           1321     1321              
  Lines          93021    93022       +1     
  Branches       11925    11925              
=============================================
- Hits           44586    44579       -7     
- Misses         42925    42930       +5     
- Partials        5510     5513       +3     

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[lollipopjin]

LGTM