channeldb: include extra data in htlc clone function

channeldb/channel.go

@@ -2440,6 +2440,7 @@ func (h *HTLC) Copy() HTLC {
 	}
 	copy(clone.Signature[:], h.Signature)
 	copy(clone.RHash[:], h.RHash[:])
+	copy(clone.ExtraData, h.ExtraData)
 
 	return clone
 }