I expected the output of "S".Pluralize(false) to be "Ss", because I see "s" appended for other letters. e.g. "K".Pluralize(false) == "Ks"

However, it throws an exception:

System.IndexOutOfRangeException: Index was outside the bounds of the array.
at System.String.get_Chars(Int32 index)
at Humanizer.Inflections.Vocabulary.MatchUpperCase(String word, String replacement) in //src/Humanizer/Inflections/Vocabulary.cs:line 158
at Humanizer.Inflections.Vocabulary.ApplyRules(IList`1 rules, String word, Boolean skipFirstRule) in //src/Humanizer/Inflections/Vocabulary.cs:line 148
at Humanizer.Inflections.Vocabulary.Pluralize(String word, Boolean inputIsKnownToBeSingular) in //src/Humanizer/Inflections/Vocabulary.cs:line 85
at Humanizer.InflectorExtensions.Pluralize(String word, Boolean inputIsKnownToBeSingular) in //src/Humanizer/InflectorExtensions.cs:line 42

Found in Humanizer.Core 2.14.1