Deleting default clause from case block deletes the wrong clause

Description:

When using a Case block, the wrong clause is deleted if you try to delete the default clause.

Desired behaviour:

Trying to delete the default block should either

a) delete the default block, or

b) warn the user that deleting the default block can cause the wf to fail, and then ask for confirmation, or

c) warn the user that the default block cannot be deleted

Steps to repro:

• add a case block

• add an additional clause

• click the default clause

• select delete

• the non-default clause is deleted instead of the default clause