Changed how children array is tested for valid objects.
Changed how children array is tested for valid objects.

numpy.where yields different results with numpy v1.9 and v1.8
for object arrays containing 'None'.

cheral/orange3,cheral/orange3,marinkaz/orange3,marinkaz/orange3,qusp/orange3,qPCR4vir/orange3,marinkaz/orange3,cheral/orange3,qusp/orange3,qusp/orange3,cheral/orange3,cheral/orange3,kwikadi/orange3,marinkaz/orange3,qPCR4vir/orange3,kwikadi/orange3,kwikadi/orange3,qPCR4vir/orange3,qPCR4vir/orange3,kwikadi/orange3,qPCR4vir/orange3,qPCR4vir/orange3,qusp/orange3,kwikadi/orange3,marinkaz/orange3,kwikadi/orange3,marinkaz/orange3,cheral/orange3