Another handler for undefined

lib/routes/comment.js

@@ -62,7 +62,7 @@ module.exports = function(crowi, app) {
     var revisionId = form.revision_id;
     var comment = form.comment;
     var position = form.comment_position || -1;
-    var isMarkdown = form.is_markdown;
+    var isMarkdown = form.is_markdown || false;
 
     return Comment.create(pageId, req.user._id, revisionId, comment, position, isMarkdown)
       .then(function(createdComment) {