I have a customer bug where they created a diagram in our tool.  However when we try and reload it, The DiagramDocument is showing there is no active layer when I try to operate on it.   We are using ver. 10.6.23.12.

I'm trying to figure out what is wrong with the document so I can guess how it got that way.  

What kinds of things could cause a document to get in that state?  Was it persisted malformed?

(Attached in an example of the bad document.)

Thanks in advance,
Jason