disable "textgrams" when minPrefixChars=0 AnalyzingInfixSuggester

        if (fieldName.equals("textgrams") && minPrefixChars > 0) {
          TokenFilter filter = new EdgeNGramTokenFilter(components.getTokenStream(), 1, minPrefixChars);
          return new TokenStreamComponents(components.getTokenizer(), filter);
        } else {
          return components; // threre is no sense to go here if minPrefixChars==0 and fieldName=="textgrams"
        }