Fix typo and improve error message in ripple writer

[ericpre]

Progress of the PR

• Fix typo and improve error message in ripple writer,
• [n/a] update docstring (if appropriate),
• [n/a] update user guide (if appropriate),
• add a changelog entry in the upcoming_changes folder (see upcoming_changes/README.rst),
• Check formatting of the changelog entry (and eventual user guide changes) in the docs/readthedocs.org:rosettasciio build of this PR (link in github checks)
• [n/a] add tests,
• ready for review.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.23%. Comparing base (46c5c5b) to head (09ce2ac).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #251      +/-   ##
==========================================
- Coverage   86.36%   86.23%   -0.14%     
==========================================
  Files          83       83              
  Lines       10652    10653       +1     
  Branches     2322     2322              
==========================================
- Hits         9200     9187      -13     
- Misses        935      949      +14     
  Partials      517      517              

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