esp8266/modnetwork: Raise ValueError when getting invalid WLAN id.
esp8266/modnetwork: Raise ValueError when getting invalid WLAN id.

Instead of crashing due to out-of-bounds array access.  Fixes #3348.

trezor/micropython,henriknelson/micropython,MrSurly/micropython,kerneltask/micropython,henriknelson/micropython,bvernoux/micropython,adafruit/circuitpython,trezor/micropython,tobbad/micropython,pozetroninc/micropython,kerneltask/micropython,trezor/micropython,swegener/micropython,pozetroninc/micropython,bvernoux/micropython,adafruit/circuitpython,kerneltask/micropython,dmazzella/micropython,bvernoux/micropython,dmazzella/micropython,swegener/micropython,trezor/micropython,tralamazza/micropython,pramasoul/micropython,pramasoul/micropython,henriknelson/micropython,adafruit/circuitpython,pramasoul/micropython,tralamazza/micropython,pfalcon/micropython,trezor/micropython,tobbad/micropython,MrSurly/micropython,pfalcon/micropython,selste/micropython,adafruit/circuitpython,swegener/micropython,adafruit/micropython,pramasoul/micropython,swegener/micropython,MrSurly/micropython,adafruit/circuitpython,kerneltask/micropython,adafruit/micropython,MrSurly/micropython,dmazzella/micropython,MrSurly/micropython,pozetroninc/micropython,selste/micropython,dmazzella/micropython,pozetroninc/micropython,adafruit/micropython,adafruit/micropython,pfalcon/micropython,henriknelson/micropython,pfalcon/micropython,tobbad/micropython,selste/micropython,bvernoux/micropython,henriknelson/micropython,tobbad/micropython,tralamazza/micropython,kerneltask/micropython,adafruit/circuitpython,bvernoux/micropython,selste/micropython,tralamazza/micropython,adafruit/micropython,tobbad/micropython,pramasoul/micropython,swegener/micropython,pozetroninc/micropython,selste/micropython,pfalcon/micropython