Add check for empty passphrase to Wifi.begin(_ssid, _pass)

[thomasvdv]

WiFi.cpp
line 98-116

Board: Arduino UNO R4 Wifi

Connections to an open network will fail, when Wifi.begin(_ssid, _pass) is called with an empty String. Some client (e.g. Arduino Cloud) allow the passphrase to be empty when configuring the network. This empty field is then passed on as "" to Wifi.begin(_ssid, _pass), resulting in a connection failure. Can you add a check for this condition and call Wifi.begin(_ssid) instead?

Related Issue: arduino-libraries/Arduino_ConnectionHandler#114