Segfault when repeatedly redefining a spinw object with temporary numpy arrays

[mducle]

This code will cause a segfault if run repeatedly:

from pyspinw import Matlab
import numpy as np
m = Matlab()

lat = [5.408, 5.4599, 19.266]
swo = m.spinw()
swo.genlattice('lat_const', np.array(lat) * np.array([2, 2, 1]), 'angled', [90, 90, 90], 'spgr', 'x,y+1/2,-z')
swo.addatom('r', [0, 0, 0], 'label', 'MCu2')

If the second last line is changed to:

swo.genlattice('lat_const', [5.408*2, 5.4599*2, 19.266], 'angled', [90, 90, 90], 'spgr', 'x,y+1/2,-z');

the segfault does not occur. The segfault also does not occur for a simple pass-through, e.g.

from pyspinw import Matlab
import numpy as np
m = Matlab()

iden = m.str2func('@(x)x')
lat = [5.408, 5.4599, 19.266]
x = m.feval(iden, np.array(lat) * np.array([2, 2, 1]))
print(x)