fix: fix to no code error

Author: azu

Diff for: src/textlint-rule-max-comma.js

@@ -22,6 +22,9 @@ export default function (context, options = defaultOptions) {
             const paragraphSentenceWithoutNode = filter(paragraphSentence, (node) => {
                 return node.type !== Syntax.Code;
             });
+            if (!paragraphSentenceWithoutNode) {
+                return;
+            }
             // This `sum(0,1,2,3,4,5,6,7,8,9,10)` is ok
             // → This  is ok
             const sentencesWithoutCode = paragraphSentenceWithoutNode

Diff for: test/textlint-rule-max-comma-test.js

@@ -6,6 +6,7 @@ const tester = new TextLintTester();
 // ruleName, rule, { valid, invalid }
 tester.run("no-todo", rule, {
     valid: [
+        "``", // no content
         // no match
         "This is text.",
         // 4 is ok by default