fix: improve undefined error handling

Author: azu

src/textlint-rule-max-comma.js

@@ -28,8 +28,8 @@ export default function (context, options = defaultOptions) {
             // This `sum(0,1,2,3,4,5,6,7,8,9,10)` is ok
             // → This  is ok
             const sentencesWithoutCode = paragraphSentenceWithoutNode
-                .children
-                .filter(node => node.type === SentenceSyntax.Sentence);
+                ?.children
+                ?.filter(node => node.type === SentenceSyntax.Sentence) ?? [];
             sentencesWithoutCode.forEach(sentence => {
                 const source = new StringSource(sentence);
                 const sentenceValue = source.toString();