perf: downgrade code for old node

Author: Scrum

index.js

@@ -113,7 +113,7 @@ function postHTMLParser(html, options) {
         return;
       }
 
-      if (last.content?.length && typeof last.content[last.content.length - 1] === 'string') {
+      if (last.content && last.content.length && typeof last.content[last.content.length - 1] === 'string') {
         last.content[last.content.length - 1] = last.content[last.content.length - 1] + text
         return
       }