Workflow cancel button does not work

1. create a new workflow
2. drag and drop a task
3. open the Task
4. click the Transitions tab
5. click several times the Add transition button
6. click Cancel
7. open the task again
8. click the Transitions tab
9. observe the empty transitions are still present

Expected behavior: when clicking Cancel the status should be identical to the one when opening the task. This means no transitions should be present any longer.