fix : when nacos push empty service instance list, should skip generate

[Erica177]

Ⅰ. Describe what this PR did

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[johnlanni]

LGTM

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.71%. Comparing base (ef31e09) to head (4d6614f).
Report is 482 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2144      +/-   ##
==========================================
+ Coverage   35.91%   45.71%   +9.80%     
==========================================
  Files          69       79      +10     
  Lines       11576    12895    +1319     
==========================================
+ Hits         4157     5895    +1738     
+ Misses       7104     6652     -452     
- Partials      315      348      +33     

see 77 files with indirect coverage changes

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