Issues with personalized content

Description

Steps to reproduce:
1. Make sure you have a personalized group with some personalized content in it (using visitor groups) on a contentarea.
2. Drag a new block into the content area of the personalized group
3. Personalize the new block to a given visitor group
4. Publish the changes
5. Go back to see the personalization of the newly added block

Expected:
It should still be personalized

Actual:
It has reset its personalization to its default value, and is thus visible to everyone.
If the editors repeat step 3 and 4, the personalization is persisted and kept.