From cc8b3f96571ea31fc69925298734cb36b07b3b28 Mon Sep 17 00:00:00 2001
From: Kris Nuttycombe <kris@nutty.land>
Date: Fri, 8 Apr 2022 14:54:23 -0600
Subject: [PATCH] Ensure pindexPrev is not null before mining against it.

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

diff --git a/src/miner.cpp b/src/miner.cpp
index 500ab7636..677411b43 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -922,7 +922,17 @@ void static BitcoinMiner(const CChainParams& chainparams)
             // Create new block
             //
             unsigned int nTransactionsUpdatedLast = mempool.GetTransactionsUpdated();
-            CBlockIndex* pindexPrev = chainActive.Tip();
+            CBlockIndex* pindexPrev;
+            {
+                LOCK(cs_main);
+                pindexPrev = chainActive.Tip();
+            }
+
+            // If we don't have a valid chain tip to work from, wait and try again.
+            if (pindexPrev == nullptr) {
+                MilliSleep(1000);
+                continue;
+            }
 
             unique_ptr<CBlockTemplate> pblocktemplate(CreateNewBlock(chainparams, minerAddress));
             if (!pblocktemplate.get())