Unable to obtain the status of missiles launched by aircraft

[cjmdd]

we can fire missiles successfully, but we are unable to obtain the status of missiles launched by aircraft:
planes=df.get_planes_list() #4ally and 4oppo
slots=df.get_missiles_device_slots_state[planes[0]]
missiles=df.get_machine_missiles_list(planes[0])
df.set_target_id(planes[0],planes[-1])
df.fire_missiles(planes[0],slots[0]) # successful

missile_state=df.get_missile_state(missiles[0])

return sates=json.loads(......)

AttributeError:'NoneType' object has no attribute decode