PackMLStatusObjectType- References causes an null exception

## Describe the bug

```txt
"CAS.UA.ModelDesigner";Error;111680094;"In UI an error has been encountered Object reference not set to an instance of an object.";;;;;"2021-07-05T09:58:40.4008318Z";;
```

## To Reproduce

Select the reference on the tree.

## Screenshots


![Untitled](https://user-images.githubusercontent.com/11937915/124457015-a302e280-dd8b-11eb-8307-6a99c2b5cade.png)

