Adding subsegments to a segment removes lists from the subsegments

[bcb37]

Version where bug was found:
6.6

Describe the bug
Attempting to add an ancestor segment to a segment's list will result in the ancestor's list being deletes

To Reproduce
Steps to reproduce the behavior:

1. Create a segment and add a list to it
2. Create another segment and add the first segment as a list to that segment
3. It will have removed the list.

Expected behavior
The subsegment will remain as it was