fix for #4111 do not ignore empty value when we construct servicename

[uglycow]

What is the purpose of the change

XXXXX

Brief changelog

fix for #4111

do not ignore empty value when we construct servicename

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #4112 into master will increase coverage by <.01%.
The diff coverage is 0%.

@@             Coverage Diff              @@
##             master    #4112      +/-   ##
============================================
+ Coverage     62.63%   62.64%   +<.01%     
- Complexity      543      545       +2     
============================================
  Files           762      762              
  Lines         32752    32753       +1     
  Branches       5162     5162              
============================================
+ Hits          20515    20517       +2     
+ Misses         9876     9875       -1     
  Partials       2361     2361

Impacted Files	Coverage Δ	Complexity Δ
...org/apache/dubbo/registry/nacos/NacosRegistry.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...bo/rpc/cluster/support/FailbackClusterInvoker.java	67.21% <0%> (-3.28%)	0% <0%> (ø)
...pache/dubbo/registry/support/AbstractRegistry.java	78.54% <0%> (-3.07%)	0% <0%> (ø)
...e/dubbo/remoting/transport/netty/NettyChannel.java	62.35% <0%> (+4.7%)	21% <0%> (+1%)	⬆️
...che/dubbo/remoting/transport/mina/MinaChannel.java	53.94% <0%> (+10.52%)	17% <0%> (+1%)	⬆️

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[Moriadry-zz]

I believe if no ignore empty value, two provider with same service but different config still get different service name, Is that true?

[chickenlj]

LGTM

[ralf0131]

LGTM.