Increase test coverage for src/sentences/utils.rs

[trkohler]

connect: https://github.com/AeroRust/nmea/issues/25

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 77.93%. Comparing base (5675768) to head (4a9bb7b). Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #130   +/-   ##
=======================================
  Coverage   77.93%   77.93%           
=======================================
  Files          37       37           
  Lines        1405     1405           
=======================================
  Hits         1095     1095           
  Misses        310      310           

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