Freeze when replacing references with more than one reference

If the user tries to replace a reference to a variable with multiple wires (one that should break and one that shouldn't) the Editor freezes up.

1. Open the Editor
2. Create a new widget blueprint
3. Name it WidgetA
4. Create a new widget blueprint
5. Name it WidgetB
6. Open WidgetA
7. Create a new event dispatcher
8. Add two variables to WidgetA
9. Set one as a reference to WidgetA and the other to WidgetB
10. Create the blueprint in the attached image
11. Drag and drop the WidgetB Variable on to the WidgetA reference in the graph (created above)
12. Notice that the editor freezes

Expected: The reference for WidgetA would be replaced by the reference for WidgetB
Result: The editor freezes