segfault when a required config argument is not set

[Profpatsch]

e.g. when I don’t set irc.realname in the config file:

> result/bin/irccat
2021-03-21 13:40:04 INFO main main.go:37 IRCCat  () starting...
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x14 pc=0x84ba74]

goroutine 1 [running]:
main.(*IRCCat).connectIRC(0xc00007a8c0, 0x0, 0x0, 0x3)
	github.com/irccloud/irccat/irc.go:16 +0xd4
main.main()
	github.com/irccloud/irccat/main.go:66 +0x5f7