#13 Bug when cutting edges

[Florian Lautenbacher]

- Create a new AgilPro project
- Create two activities, Activity1 and Activity2
- add an activity edge from 1 to 2
- Save it, Close it and Re-open it, It opens OK
- Select the transition
- Right click and select "cut" from the context menu
- The transition disappears from the Outline view, but it is still visible in the graph view
- Save it, Close it and Re-open it, It produces an error on opening "Value PackageImpl(...) is not legal".
- Say OK to the error dialog
- The graph is empty, but the Outline view shows the two activities.