JP-3223: Extract_2d 'slit_name' parameter fails for NRS_MSASPEC slits

[penaguerrero]

Resolves JP-3223 (again)

Closes #

This PR addresses a crash of extract_2d when user provides slit_name, and value is a string. This change had been done and merged in #8108 , but it accidentally got undone by a later PR. So note that the original fix was NOT included in DMS B10.1 as we'd assumed. It will now be included in B10.2.

Checklist for maintainers

• added entry in CHANGES.rst within the relevant release section
• updated or added relevant tests
• updated relevant documentation
• added relevant milestone
• added relevant label(s)
• ran regression tests, post a link to the Jenkins job below.
  How to run regression tests on a PR
• Make sure the JIRA ticket is resolved properly

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (d63fb5a) 75.20% compared to head (bcedbd2) 75.20%.

Files	Patch %	Lines
jwst/extract_2d/nirspec.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #8272   +/-   ##
=======================================
  Coverage   75.20%   75.20%           
=======================================
  Files         470      470           
  Lines       38581    38578    -3     
=======================================
  Hits        29013    29013           
+ Misses       9568     9565    -3     

Flag	Coverage Δ		*Carryforward flag
nightly	77.38% <ø> (ø)		Carriedforward from 2f1a34d

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[hbushouse]

Needs a regression test run.

[penaguerrero]

reg tests running at: https://plwishmaster.stsci.edu:8081/job/RT/job/JWST-Developers-Pull-Requests/1201/

[penaguerrero]

Reg tests succeeded! Only failures are due to unable to retrieve file from Artifactory.