// send an NTP request to the time server at the given address
unsigned long sendNTPpacket(IPAddress& address)
to
// send an NTP request to the time server at the given address
void sendNTPpacket(IPAddress& address)
It'll much better from now on, you turn on Arduino IDE File -> Preferences -> Settings -> Compiler Warnings to All instead of None to catch all the code issues.
Tested OK (no crash) with core v3.0.2 now after modification.