Thank you for the report. 

Yes, this is the case, in the current version. I have added a notification in the “Apply Icon pack” dialog and when you try to change an icon if the hollow bubbles are enabled. The app also switches you back to full bubbles if you choose hollow bubbles only and then change the icon. 

I cannot post images here (shortcoming of Google+) but please see my next post.

But both of these measurements are just temporary workarounds, I intend to take care of this in a future version, especially because of the case you are demonstrating, when an app doesn’t have any icon, there is nothing to fall back to.