fix(document): only skip modifying subdoc path if parent is direct mo…

…dified

Fix #4405

lib/types/subdocument.js

@@ -46,7 +46,7 @@ Subdocument.prototype.$isValid = function(path) {
 Subdocument.prototype.markModified = function(path) {
   Document.prototype.markModified.call(this, path);
   if (this.$parent) {
-    if (this.$parent.isModified(this.$basePath)) {
+    if (this.$parent.isDirectModified(this.$basePath)) {
       return;
     }
     this.$parent.markModified([this.$basePath, path].join('.'));