Zipper mesh segfault fix

[sseraj]

Purpose

This fixes the zipper mesh segfault issue first reported by @awccopp.

When creating the zipper mesh, indexing out of bounds can occur when the number of closest points we are searching for is greater than the total number of points on a string. Capping the initial nSearch in the stringMatch routine solves the issue.

The current initial value for nSearch is 50, which explains why the problem only appears on small meshes like @awccopp's airfoil cases. I added a test with a simple overset cube mesh that can reproduce the error.

Expected time until merged

Regular urgency; one week

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

Run test_zipper.py without compiling the fix. The result will be a segfault (or 'index outside of expected range' if compiled with a bounds check flag).
Run the test again after recompiling. The test should now pass.

Checklist

• I have run flake8 and black to make sure the code adheres to PEP-8 and is consistently formatted
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[codecov]

Codecov Report

Merging #193 (b11d794) into master (9266f4d) will decrease coverage by 12.55%.
The diff coverage is n/a.

❗ Current head b11d794 differs from pull request most recent head 9ae5eee. Consider uploading reports for the commit 9ae5eee to get more accurate results

@@             Coverage Diff             @@
##           master     #193       +/-   ##
===========================================
- Coverage   43.27%   30.72%   -12.56%     
===========================================
  Files          15       15               
  Lines        3561     3561               
===========================================
- Hits         1541     1094      -447     
- Misses       2020     2467      +447     

Impacted Files	Coverage Δ
adflow/pyADflow.py	46.98% <0.00%> (-20.27%)	⬇️
adflow/MExt.py	78.94% <0.00%> (-18.43%)	⬇️

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[joanibal]

Nice work Sabet!

[anilyil]

it looks like we need another approval? I tried requesting one from @joanibal since he already approved but github didnt like that

[awccopp]

I pulled your fixes and ran them locally on some cases where I had this issue and they all ran fine. Looks good to me thanks for fixing.