From 68e1a8c790ad7927ca2f76b764dde40b978e548c Mon Sep 17 00:00:00 2001
From: UdjinM6 <UdjinM6@users.noreply.github.com>
Date: Tue, 11 Apr 2017 13:54:34 +0300
Subject: [PATCH] Safety check in CInstantSend::SyncTransaction (#1412)

---
 src/instantx.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/instantx.cpp b/src/instantx.cpp
index 899ab13780..94799ff316 100644
--- a/src/instantx.cpp
+++ b/src/instantx.cpp
@@ -786,7 +786,17 @@ void CInstantSend::SyncTransaction(const CTransaction& tx, const CBlock* pblock)
     uint256 txHash = tx.GetHash();
 
     // When tx is 0-confirmed or conflicted, pblock is NULL and nHeightNew should be set to -1
-    CBlockIndex* pblockindex = pblock ? mapBlockIndex[pblock->GetHash()] : NULL;
+    CBlockIndex* pblockindex = NULL;
+    if(pblock) {
+        uint256 blockHash = pblock->GetHash();
+        BlockMap::iterator mi = mapBlockIndex.find(blockHash);
+        if(mi == mapBlockIndex.end() || !mi->second) {
+            // shouldn't happen
+            LogPrint("instantsend", "CTxLockRequest::SyncTransaction -- Failed to find block %s\n", blockHash.ToString());
+            return;
+        }
+        pblockindex = mi->second;
+    }
     int nHeightNew = pblockindex ? pblockindex->nHeight : -1;
 
     LogPrint("instantsend", "CInstantSend::SyncTransaction -- txid=%s nHeightNew=%d\n", txHash.ToString(), nHeightNew);