FIX: Issue#1900 padstacks def

[svandenb-dev]

this PR is fixing issue #1900 when user defines padstacks definition without layers (e.g. only a hole) definition were not returned by edb.padstacks.definition manager.

closes #1900

[codecov-commenter]

Codecov Report

❌ Patch coverage is 78.57143% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.73%. Comparing base (5cbae21) to head (3899241).
⚠️ Report is 47 commits behind head on main.

❌ Your patch status has failed because the patch coverage (78.57%) is below the target coverage (85.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1948      +/-   ##
==========================================
+ Coverage   70.20%   70.73%   +0.53%     
==========================================
  Files         261      263       +2     
  Lines       42416    42888     +472     
==========================================
+ Hits        29779    30338     +559     
+ Misses      12637    12550      -87     

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