Undo-Redo-Bug

[Thomas-S]

1. Create a new *.sad-File
2. Create two ensembles "Father" and "Mother"
3. Create "Son" inside "Father"
4. Select "Father", pull the outgoing arrow inside "Father" and select "Create Note Attachment To" -> "New Element: Note"
5. Create an Incoming-Constraint from "Son" to "Mother"
6. Delete "Father"
7. Delete "Mother"
8. Do "Undo" twice.
9. Do Undo again and the following error message occurs: "Abnormal Workbench Condition java.lang.NullPointerException"

This also erases the entire Undo-Redo-Trace and if one deletes "Father" again, the Incoming-Constraint won't disappear.

[theokischka]

couldnt recreate this behaviour. after undoing deletion of mother and father undoing the creation of the incoming constraint worked properly.

[Alwe]

Undo of constraint creation is broken.

I think this is issue can be simplified to:

1. Create constraint
2. Undo