Update assets/inc/class.MCB.php
Update assets/inc/class.MCB.php

Only show the meta box if the post has saved blocks, which should happen after it has been saved the first time.
Update assets/inc/class.MCB.php

Hmm. Probably the intent of the original code is to show the meta box when the page cannot be fetched locally so that the user will see the error message.

This is probably what is needed to fix my original issue with the meta box appearing with an erroneous error message for a private custom post type.
Merge pull request #7 from Mrnt/master

Fix for issue #6: 'Problem with meta box appearing for private custom post types?'