Fix clang warning on clang14

[paleolimbot]

As shown here: https://cran.r-project.org/web/checks/check_results_s2.html

Fixes #167.

[codecov-commenter]

Codecov Report

Merging #172 (cb64ef2) into main (5c3f27f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #172   +/-   ##
=======================================
  Coverage   93.93%   93.93%           
=======================================
  Files          49       49           
  Lines        3463     3463           
=======================================
  Hits         3253     3253           
  Misses        210      210           

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