Avoid NPE for handling client settings null in notifyClientTermination

[lollipopjin]

Which Issue(s) This PR Fixes

Avoid NPE for handling client settings null in notifyClientTermination

[qianye1001]

LGTM

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.

Project coverage is 48.06%. Comparing base (586a274) to head (f5103b7).

Files with missing lines	Patch %	Lines
.../rocketmq/proxy/grpc/v2/client/ClientActivity.java	0.00%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #9308      +/-   ##
=============================================
- Coverage      48.12%   48.06%   -0.06%     
+ Complexity     12140    12118      -22     
=============================================
  Files           1322     1322              
  Lines          93237    93242       +5     
  Branches       11957    11958       +1     
=============================================
- Hits           44868    44816      -52     
- Misses         42830    42881      +51     
- Partials        5539     5545       +6     

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[fuyou001]

LGTM