Fix the case where the index of d becomes negative. see https://wiki.csiro.au/display/taxamatch/The+MDLD+(Modified+Damerau-Levenshtein+Distance)+Algorithm
Fix the case where the index of d becomes negative.
see https://wiki.csiro.au/display/taxamatch/The+MDLD+(Modified+Damerau-Levenshtein+Distance)+Algorithm

GlobalNamesArchitecture/damerau-levenshtein,GlobalNamesArchitecture/damerau-levenshtein