[NONEVM-3303] [COT-01] Nil Pointer Dereference In Trace Tracking Causes Client Crash (#478)

* fix: receivedMessage could be nil if channel closed

* fix: lint

* fix: handle context

Author: patricios-space

pkg/ton/tracetracking/message.go

@@ -2,6 +2,7 @@ package tracetracking
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"math/big"
 
@@ -342,23 +343,37 @@ func (m *ReceivedMessage) WaitForOutgoingMessagesToBeReceived(ctx context.Contex
 		transactionsReceived := make(chan *tlb.Transaction)
 		go c.SubscribeOnTransactions(ctx, sentMessage.InternalMsg.DstAddr, m.LamportTime, transactionsReceived)
 
-		var receivedMessage *ReceivedMessage
-		for rTX := range transactionsReceived {
+		receivedMessage, err := waitForMatchingMessage(ctx, transactionsReceived, sentMessage)
+		if err != nil {
+			return err
+		}
+		m.OutgoingInternalReceivedMessages = append(m.OutgoingInternalReceivedMessages, receivedMessage)
+	}
+
+	return nil
+}
+
+func waitForMatchingMessage(ctx context.Context, transactionsReceived chan *tlb.Transaction, sentMessage *SentMessage) (*ReceivedMessage, error) {
+	for {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case rTX, ok := <-transactionsReceived:
+			if !ok {
+				return nil, errors.New("transaction channel closed")
+			}
+
 			if rTX.IO.In != nil && rTX.IO.In.MsgType == tlb.MsgTypeInternal {
-				var err error
-				receivedMessage, err = sentMessage.MapToReceivedMessageIfMatches(rTX)
+				receivedMessage, err := sentMessage.MapToReceivedMessageIfMatches(rTX)
 				if err != nil {
-					return fmt.Errorf("failed to process incoming message: %w", err)
+					return nil, fmt.Errorf("failed to process incoming message: %w", err)
 				}
 				if receivedMessage != nil {
-					break
+					return receivedMessage, nil
 				}
 			}
 		}
-		m.OutgoingInternalReceivedMessages = append(m.OutgoingInternalReceivedMessages, receivedMessage)
 	}
-
-	return nil
 }
 
 // MapToReceivedMessageIfMatches checks if a transaction corresponds to the reception