Allow joining hidden WiFi on micropython devices (ignore Authmode detection error)

[nznobody]

make not detecting authmode an acceptable error to getting wifi going. Getting Auth mode fails on hidden networks as it does not show in the scan

[nznobody]

It appears that auth_mode may be None, although the documentation is unclear on the consequences of this. In real world testing, this works and the device connects (tested with hidden WPA2 network).

[1] https://docs.pycom.io/firmwareapi/pycom/network/wlan/

[amotl]

Thanks a stack again!