Attaching a field of a node type in another form
"EntityMalformedException: Missing bundle property on entity of type node."
means that Drupal does not recognize your entity as a valid one. In the entity info listing, there is a mapping from "bundle" to "type", for nodes.

Either your $node doesn't have a -&gt;type, or Drupal no longer has the type registered. The type could have been removed, either from the UI, or by disabling a feature, and possibly in more interesting ways as well.