service: prevent nil deref in validate with wrapped join request (#4547)

When a client hits /rtc/v[01]/validate with a base64 WrappedJoinRequest
whose embedded JoinRequest.ClientInfo is unset, validateInternal called
AugmentClientInfo with a nil *ClientInfo and panicked at ci.Address =
GetClientIP(req). The non-wrapped branch already allocates via
ParseClientInfo; do the same here so pi.Client always gets at least the
resolved client Address.

pkg/service/rtcservice.go

@@ -254,6 +254,9 @@ func (s *RTCService) validateInternal(
 	} else {
 		lgr.Debugw("processing join request", "joinRequest", logger.Proto(joinRequest))
 
+		if joinRequest.ClientInfo == nil {
+			joinRequest.ClientInfo = &livekit.ClientInfo{}
+		}
 		AugmentClientInfo(joinRequest.ClientInfo, r)
 		pi.Client = joinRequest.ClientInfo