change target to pointer and check for association

[raphaeldussin]

update from #529

attempting to solve problem raised by @gustavo-marques in mom-ocean#1616

[codecov]

Codecov Report

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

Comparison is base (7ef6a57) 37.45% compared to head (78e2c88) 37.45%.

Files	Patch %	Lines
...parameterizations/vertical/MOM_set_diffusivity.F90	0.00%	0 Missing and 1 partial ⚠️
...rc/parameterizations/vertical/MOM_tidal_mixing.F90	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                          Coverage Diff                           @@
##           dev-gfdl-main-candidate-2023-11-13     #530      +/-   ##
======================================================================
- Coverage                               37.45%   37.45%   -0.01%     
======================================================================
  Files                                     270      270              
  Lines                                   79765    79765              
  Branches                                14831    14833       +2     
======================================================================
- Hits                                    29879    29878       -1     
  Misses                                  44350    44350              
- Partials                                 5536     5537       +1     

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[alperaltuntas]

This PR fixes the issue we encountered. Thanks!

[marshallward]

This passed our regression after merge into the candidate branch: https://gitlab.gfdl.noaa.gov/ogrp/MOM6/-/pipelines/21587

I will merge it in once this MacoS FPE issue has gone away (one way or another).