check

index.mjs

@@ -528,7 +528,7 @@ function buildAST(md, mdTags=syntax, offset=0, tree={tag: 'root'}, stack=[]){
         const {[index]: titleContent } = currentNode.startMatch
         if (titleContent && recursive){
             currentNode.title = buildAST(titleContent, mdTags).children
-            currentNode.title.forEach(item => item.parent = currentNode)
+            currentNode.title.forEach(item => (typeof item === 'object') && item.parent = currentNode)
         }
         else {
             currentNode.title = [titleContent]