fix less than 1nm issue

[joamatab]

No description provided.

[sourcery-ai]

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[codecov]

Codecov Report

Attention: Patch coverage is 7.14286% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 68.25%. Comparing base (fae9f6c) to head (8e3d320).
Report is 2 commits behind head on main.

Files	Patch %	Lines
gdsfactory/add_ports.py	0.00%	13 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2811   +/-   ##
=======================================
  Coverage   68.25%   68.25%           
=======================================
  Files         300      300           
  Lines       15594    15595    +1     
  Branches     2276     2276           
=======================================
+ Hits        10643    10644    +1     
  Misses       4357     4357           
  Partials      594      594           

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