Error loading viewer template xml files from v3.x to v4.x

We are in the process of upgraging to essentials 4.0.2 from 3.15.1.

After copying one of our site folders from the old version environment to new, then upgrading the viewer and launching, we get an error rooted in the viewer config file. This error stems from the viewer trying to reference viewer template .xml files; set under the "Look and Feel"/"Theme" section in essentials manager (ex: DarkGray, Default, Forest, Misty Rose, etc).

In essentials 4.0.2 there only appear to be 2 themes. All of the rest of the themes do not appear, and therefore do not suggest forward compatability (no DarkGray, Forest, Misty Rose) . So, if you do not have one of the themes that are still supported in 4.0.2, your viewer will search for the template .xml with no luck and promptly provide an error. You have to manually go into the viewer config file and delete the remnant template .xml reference. Make sure you take care of the back up file as well.

Perhaps this could issue could be remedied with subsequent released of essentials v4.x ?

Seems we shouldn't have to dig into the xml files for this type of feature during upgrades.