From be7d77bd5d82cdd52314b2aedaa0530260b7a709 Mon Sep 17 00:00:00 2001
From: Josh Rickmar <jrick@companyzero.com>
Date: Tue, 8 Aug 2023 21:11:31 +0000
Subject: [PATCH] handle nil mix tx better in cm message

---
 wire/msgmixcm.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/wire/msgmixcm.go b/wire/msgmixcm.go
index 92465d7939..92a8910f83 100644
--- a/wire/msgmixcm.go
+++ b/wire/msgmixcm.go
@@ -105,6 +105,10 @@ func (msg *MsgMixCM) writeMessageNoSignature(op string, w io.Writer, pver uint32
 		return err
 	}
 
+	if msg.Mix == nil {
+		msg := fmt.Sprintf("nil mix transaction")
+		return messageError(op, ErrInvalidMsg, msg)
+	}
 	err = msg.Mix.BtcEncode(w, pver)
 	if err != nil {
 		return err
@@ -201,6 +205,10 @@ func (msg *MsgMixCM) GetRun() uint32 {
 func NewMsgMixCM(identity [33]byte, sid [32]byte, expiry int64, run uint32,
 	mix *MsgTx, seenDCs []chainhash.Hash) *MsgMixCM {
 
+	if mix == nil {
+		mix = NewMsgTx()
+	}
+
 	return &MsgMixCM{
 		Identity:  identity,
 		SessionID: sid,