Impossible to move on canvas when using addEdgeMode sometimes

[GitHubish]

I have a bug that only occurs when following a succession of fairly simple actions, but which is really blocking. The principle is that I want to be able to trace a link between two nodes, but the destination node is out of scope. Here's how to reproduce the problem on this example.

1. I move a node
2. I switch to addEdgeMode
3. I start tracing an edge from a node but end up releasing it on an empty zone
4. I try to move the "visible zone" of the canvas and it shakes and prevents me from moving the zone

If physic is on, the "selected" node shakes, but if physic is off, it moves the node on which I started the tracing operation and doesn't let me move the canvas, which is problematic because that's the operation I want to perform.