Dragging an expanded group in the blackboard collapses it until releasing

Steps to reproduce:

1. In any graph, create a variable
2. Create a group
3. Create a variable within in the group
4. Drag the group to the bottom of the blackboard
5. Collapse the group
6. Expand the group
7. Drag the group to the top of the blackboard

Actual results: While dragging, the group is collapsed

Expected results: The group stays expanded during and after the dragging operation

Reproducible with versions: 
0.2.0-exp.1 (6.3a4; 6.2b12)

Tested on (OS): MacOS