Skip list/type A mode arguments

Type-A modes always have an argument[0], but soju doesn't care about
them since it doesn't keep track of mode lists (ban/invite/.. lists).

[0] https://modern.ircdocs.horse/#mode-message
> Type A: Modes that add or remove an address to or from a list. These
> modes MUST always have a parameter when sent from the server to a
> client.

irc.go

@@ -145,7 +145,9 @@ outer:
 		if !ok {
 			continue
 		}
-		if mt == modeTypeB || (mt == modeTypeC && plusMinus == '+') {
+		if mt == modeTypeA {
+			nextArgument++
+		} else if mt == modeTypeB || (mt == modeTypeC && plusMinus == '+') {
 			if plusMinus == '+' {
 				var argument string
 				// some sentitive arguments (such as channel keys) can be omitted for privacy