From 8e1ba0658d10a620b0d1e382ebc751170eb23f34 Mon Sep 17 00:00:00 2001
From: Duke Leto <duke@leto.net>
Date: Sun, 18 Sep 2022 10:27:48 -0400
Subject: [PATCH] Ensure pindexPrev is not null before mining against it in
 both BitcoinMiner and RandomXMiner

---
 src/miner.cpp | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/miner.cpp b/src/miner.cpp
index 16c18146b..72d6d04df 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -1102,6 +1102,14 @@ void static RandomXMiner()
             // Create new block
             unsigned int nTransactionsUpdatedLast = mempool.GetTransactionsUpdated();
             CBlockIndex* pindexPrev = chainActive.LastTip();
+
+            // If we don't have a valid chain tip to work from, wait and try again.
+            if (pindexPrev == nullptr) {
+                fprintf(stderr,"%s: null pindexPrev, trying again...\n",__func__);
+                MilliSleep(1000);
+                continue;
+            }
+
             if ( Mining_height != pindexPrev->GetHeight()+1 )
             {
                 Mining_height = pindexPrev->GetHeight()+1;
@@ -1460,6 +1468,14 @@ void static BitcoinMiner()
             //
             unsigned int nTransactionsUpdatedLast = mempool.GetTransactionsUpdated();
             CBlockIndex* pindexPrev = chainActive.LastTip();
+
+            // If we don't have a valid chain tip to work from, wait and try again.
+            if (pindexPrev == nullptr) {
+                fprintf(stderr,"%s: null pindexPrev, trying again...\n",__func__);
+                MilliSleep(1000);
+                continue;
+            }
+
             if ( Mining_height != pindexPrev->GetHeight()+1 )
             {
                 Mining_height = pindexPrev->GetHeight()+1;