Network Explorer: crashes mid optimization

[ajdapretnar]

Network version

1.6.0

Orange version

3.30.2dev

Expected behavior

Orange doesn't crash.

Actual behavior

Orange crashes with Abort trap and the below error.

------------------- TypeError Exception (in non-GUI thread) -------------------
Traceback (most recent call last):
  File "/Users/ajda/orange/orange3-network/orangecontrib/network/widgets/OWNxExplorer.py", line 649, in run
    self.done.emit(widget.positions)
TypeError: LayoutOptimizer.done[numpy.ndarray].emit(): argument 1 has unexpected type 'NoneType'
-------------------------------------------------------------------------------

Steps to reproduce the behavior

Playing around with Corpus to Network parameters. I assume it happens once an existing computation is not yet finished.

Additional info (worksheets, data, screenshots, ...)