Stunner - Unkown Custom tasks in Designer makes Diagram Explorer empty

Summary
Unknown Custom tasks in BPMN Designer makes Diagram Explorer empty.

In Standalone editors:

• you can remove the WID for the custom task and upon reopenning the diagram explorer will be gone.
• open BPMN file that has Custom tasks and there is no WID present in workspace at expected places.

For VSCode it is the same

Workaround is to use known custom tasks. Known by editor. (There is a WID in workspace).

Issue is also fixed when you delete the unknown custom task from designer.