Fix urls may be null, and NullPointerException will be thrown in ConfigValidationUtils (#8020)

[skyguard1]

What is the purpose of the change

Fix urls may be null, and NullPointerException will be thrown in ConfigValidationUtils
In this issue(#8020 ), this pr is to fix this issue, to avoid throwing NullPointerException in ConfigValidationUtils, thanks

Fixes #8020

Brief changelog

Verifying this change

Checklist

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[xiaoheng1]

In my opinion, this place address should not be empty, if it is empty, an exception should be thrown

[codecov-commenter]

Codecov Report

Merging #8021 (21e2f08) into master (584ab28) will increase coverage by 0.04%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master    #8021      +/-   ##
============================================
+ Coverage     61.02%   61.07%   +0.04%     
- Complexity      489      490       +1     
============================================
  Files          1090     1090              
  Lines         43951    43953       +2     
  Branches       6423     6424       +1     
============================================
+ Hits          26822    26843      +21     
+ Misses        14151    14124      -27     
- Partials       2978     2986       +8     

Impacted Files	Coverage Δ
...ache/dubbo/config/utils/ConfigValidationUtils.java	73.33% <0.00%> (-0.50%)	⬇️
...port/identifier/BaseServiceMetadataIdentifier.java	57.14% <0.00%> (-3.58%)	⬇️
...apache/dubbo/common/extension/ExtensionLoader.java	80.81% <0.00%> (-0.43%)	⬇️
...ting/zookeeper/curator/CuratorZookeeperClient.java	70.68% <0.00%> (+1.14%)	⬆️
.../src/main/java/org/apache/dubbo/rpc/RpcStatus.java	73.80% <0.00%> (+1.19%)	⬆️
...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%)	⬆️
...etadata/report/support/AbstractMetadataReport.java	59.70% <0.00%> (+2.42%)	⬆️
...o/remoting/transport/ChannelHandlerDispatcher.java	70.00% <0.00%> (+10.00%)	⬆️
...che/dubbo/remoting/transport/mina/MinaChannel.java	46.05% <0.00%> (+10.52%)	⬆️

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