[master] fix NPE in doOverrideIfNecessary

[zrlw]

What is the purpose of the change

fix #8765 on master

[codecov-commenter]

Codecov Report

Merging #8837 (199e397) into master (f8f6995) will increase coverage by 0.02%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master    #8837      +/-   ##
============================================
+ Coverage     61.05%   61.08%   +0.02%     
  Complexity      449      449              
============================================
  Files          1100     1100              
  Lines         44422    44422              
  Branches       6469     6469              
============================================
+ Hits          27124    27137      +13     
+ Misses        14314    14294      -20     
- Partials       2984     2991       +7     

Impacted Files	Coverage Δ
...e/dubbo/registry/integration/RegistryProtocol.java	67.17% <0.00%> (+4.86%)	⬆️
...pache/dubbo/registry/support/AbstractRegistry.java	78.88% <0.00%> (-1.49%)	⬇️
...pache/dubbo/registry/support/FailbackRegistry.java	64.05% <0.00%> (-0.93%)	⬇️
...g/apache/dubbo/registry/consul/ConsulRegistry.java	60.00% <0.00%> (-0.59%)	⬇️
...apache/dubbo/common/extension/ExtensionLoader.java	80.89% <0.00%> (-0.22%)	⬇️
...mon/src/main/java/org/apache/dubbo/common/URL.java	55.24% <0.00%> (+0.21%)	⬆️
...e/dubbo/remoting/transport/netty4/NettyClient.java	71.01% <0.00%> (+1.44%)	⬆️
.../dubbo/remoting/transport/netty4/NettyChannel.java	64.35% <0.00%> (+1.98%)	⬆️

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[changfubai]

LGTM