bad argument #1 to 'type' (string expected, got nil)

[Sorinaki]

I'm not at all good with lua, so I don't quite get it how local wireless_status = conn:call("network.wireless", "status", {}) parses the devices, but a little dbg on line 401 shows that the radio1 returns nothing.
Any idea why iface.ifnames returns nil?

wifi-disconnect-low-signal: radio1: Device nil Section default_radio1
/usr/bin/lua: /usr/bin/wifi-disconnect-low-signal.lua:201: bad argument #1 to 'type' (string expected, got nil)
stack traceback:
[C]: in function 'type'
/usr/bin/wifi-disconnect-low-signal.lua:201: in function 'new'
/usr/bin/wifi-disconnect-low-signal.lua:404: in function 'get_wifi_devices'
/usr/bin/wifi-disconnect-low-signal.lua:438: in main chunk
[C]: ?