Can't supply argument bs != None to gt.minimize_nested_blockmodel_dl

I'm running latest version, installed via Ubuntu's apt-get.

I want to initialize the nested state with a given hierarchy. The following of course is pointless, but is how the mechanics should work (?):

>>> from graph_tool import *
>>> import graph_tool.all as gt
>>> g = gt.collection.data["football"]
>>> g
<Graph object, undirected, with 115 vertices and 613 edges at 0x7fe79ade6630>
>>> state = gt.minimize_nested_blockmodel_dl(g)
>>> bs = state.get_bs()
>>> state2 = gt.minimize_nested_blockmodel_dl(g, bs=bs)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/graph_tool/inference/minimize.py", line 503, in minimize_nested_blockmodel_dl
    base_type=type(min_state),
UnboundLocalError: local variable 'min_state' referenced before assignment