fix 'get_desc_authors' when no aut specified

[mpadge]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.66%. Comparing base (644ee32) to head (0952edf).
Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
R/cm-metric-maintainer-count.R	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #92      +/-   ##
==========================================
- Coverage   92.69%   92.66%   -0.04%     
==========================================
  Files          50       50              
  Lines        3353     3379      +26     
==========================================
+ Hits         3108     3131      +23     
- Misses        245      248       +3     

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