🐛 Fixed port routing determination for unconnected gates in the Bestagon library

[marcelwa]

Description

When using the Bestagon gate library, it was impossible to map gates without connections. This has been fixed. Many thanks to @wlambooy for reporting!

Checklist:

• The pull request only contains commits that are related to it.
• I have added appropriate tests and documentation.
• I have made sure that all CI jobs on GitHub pass.
• The pull request introduces no new warnings and follows the project's style guidelines.

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (main@40f5361). Click here to learn what that means.
The diff coverage is 66.66%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #212   +/-   ##
=======================================
  Coverage        ?   94.24%           
=======================================
  Files           ?       82           
  Lines           ?     7367           
  Branches        ?        0           
=======================================
  Hits            ?     6943           
  Misses          ?      424           
  Partials        ?        0           

Impacted Files	Coverage Δ
...clude/fiction/technology/sidb_bestagon_library.hpp	90.90% <66.66%> (ø)

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