Get rid of inconsequential numpy warning

[PhilippKaniuth]

Hunt down this warning:

python3.9/site-packages/numpy/core/fromnumeric.py:43: VisibleDeprecationWarning: Creating an ndarray from ragged nested sequences (which is a list-or-tuple of lists-or-tuples-or ndarrays with different lengths or shapes) is deprecated. If you meant to do this, you must specify 'dtype=object' when creating the ndarray.

It occurs when parallel is not 1. It doesn't have an effect on results.