When deleting a Struct Variable and undoing it, it removes all rows from related Datatables

When undoing variables in a Structure it clears the referenced Datatable of all its rows. However deleting and just adding a new variable works fine. Repeated undos have the chance to add back the rows to the Datatable.

1. Create a Structure and add a few variables to it
2. Create a Datatable referencing the Structure you made and add a few rows
3. Delete a variable in the Structure and check the Datatable to see that it was removed
4. Press Ctrl-Z to undo the variable deletion

Results: The Datatable is cleared of all rows

Expected: The Datatable adds the rows back to the deleted variable