UGENE crashes if arrow graph item leaves the scene in the Workflow Designer

Scenario to reproduce:

1. Open WD.
2. Open any sample.
3. Drag any arrow by its head.
   Expected state: the arrow is dragged, you can drop it to any output slot to connect elements.
4. Do not release mouse button, press and hold Alt key.
   Expected state: the input slot can be moved around the element's body.
   Current state: there are two modes enabled simultaneously: the slot moving and the elements connecting.
5. Drag the arrow to the scene edge.
   Current state: when the arrow leaves the scene, UGENE crashes.