From ef9a13b5572ae8a9510ed86958a4b6843b4302e1 Mon Sep 17 00:00:00 2001
From: miketout <michaeltoutonghi@gmail.com>
Date: Fri, 5 Oct 2018 21:44:24 -0700
Subject: [PATCH] Additional null check

---
 src/main.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/main.cpp b/src/main.cpp
index e08787d56..c3febbb20 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4127,7 +4127,7 @@ bool ReconsiderBlock(CValidationState& state, CBlockIndex *pindex) {
     
     // Remove the invalidity flag from this block and all its descendants.
     BlockMap::iterator it = mapBlockIndex.begin();
-    while (it != mapBlockIndex.end()) {
+    while (it != mapBlockIndex.end()  && it->second != 0) {
         if (!it->second->IsValid() && it->second->GetAncestor(nHeight) == pindex) {
             it->second->nStatus &= ~BLOCK_FAILED_MASK;
             setDirtyBlockIndex.insert(it->second);