FIX: External circuit import of renamed sources

[vpipidis]

Description

Created a check whether the source has a custom name before evaluating the label to pass as an argument on Maxwell3D.edit_external_circuit

Issue linked

#6127

Checklist

• I have tested my changes locally.
• I have added necessary documentation or updated existing documentation.
• I have followed the coding style guidelines of this project.
• I have added appropriate tests (unit, integration, system).
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved by the PR if any.
• I have agreed with the Contributor License Agreement (CLA).

[ansys-reviewer-bot]

Thanks for opening a Pull Request. If you want to perform a review write a comment saying:

@ansys-reviewer-bot review

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.16%. Comparing base (fc81bcc) to head (8fc8141).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6128      +/-   ##
==========================================
+ Coverage   85.14%   85.16%   +0.01%     
==========================================
  Files         167      167              
  Lines       63596    63602       +6     
==========================================
+ Hits        54148    54164      +16     
+ Misses       9448     9438      -10     

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Samuelopez-ansys]

Good job @vpipidis ! Your first PR, Congrats