Fix null pointer crashes causing seed node crash-loops (v5.8.1)

Guard pindexBest and pprev dereferences that segfault during IBD
block serving when chain state is incomplete:
- kernel.cpp: CheckStakeKernelHash null pindexBest during PoS validation
- main.cpp: InvalidChainFound null pprev/pindexBest on rejected blocks
- main.cpp: SetBestChain null pprev in trust calculation
- main.cpp: ProcessBlock orphan handler null pindexBest

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CMakeLists.txt

@@ -6,7 +6,7 @@ if(POLICY CMP0167)
 endif()
 
 project(Triangles
-    VERSION 5.8.0.0
+    VERSION 5.8.1.0
     DESCRIPTION "Cryptographic Triangles Wallet"
     LANGUAGES C CXX
 )

src/clientversion.h

@@ -8,7 +8,7 @@
 // These need to be macros, as version.cpp's and triangles-qt.rc's voodoo requires it
 #define CLIENT_VERSION_MAJOR       5
 #define CLIENT_VERSION_MINOR       8
-#define CLIENT_VERSION_REVISION    0
+#define CLIENT_VERSION_REVISION    1
 #define CLIENT_VERSION_BUILD       0
 
 // Converts the parameter X to a string after macro replacement on X has been performed.

src/kernel.cpp

@@ -334,9 +334,11 @@ bool CheckStakeKernelHash(unsigned int nBits, const CBlock& blockFrom, unsigned
     // Now check if proof-of-stake hash meets target protocol
     if (CBigNum(hashProofOfStake) > bnCoinDayWeight * bnTargetPerCoinDay)
     {
+        // Guard against null pindexBest during early startup / IBD
+        int nCurrentHeight = pindexBest ? pindexBest->nHeight : 0;
+
         // triangles fix: accept hash to get blockchain moving again with Pharao release (v 4.0.0.1) for first 10 blocks after release
-        //printf(">>>> pindexBest->nHeight %d\n",pindexBest->nHeight);
+        if (nCurrentHeight > CRAPCHAIN_CUTOFF_BLOCK)
-        if (pindexBest->nHeight > CRAPCHAIN_CUTOFF_BLOCK)
         {
             if(fDebug)
             {
@@ -349,8 +351,8 @@ bool CheckStakeKernelHash(unsigned int nBits, const CBlock& blockFrom, unsigned
         else
         {
             //accept hash
-            if (pindexBest->nHeight % 10000 == 0 || pindexBest->nHeight > 2186900)
+            if (nCurrentHeight % 10000 == 0 || nCurrentHeight > 2186900)
-                printf(">>>> pindexBest->nHeight %d, Pharao release - hash accepted\n", pindexBest->nHeight);
+                printf(">>>> pindexBest->nHeight %d, Pharao release - hash accepted\n", nCurrentHeight);
         }
     }
 

src/main.cpp

@@ -1504,8 +1504,12 @@ void static InvalidChainFound(CBlockIndex* pindexNew)
         uiInterface.NotifyBlocksChanged();
     }
 
-    uint256 nBestInvalidBlockTrust = pindexNew->nChainTrust - pindexNew->pprev->nChainTrust;
+    uint256 nBestInvalidBlockTrust = pindexNew->pprev
-    uint256 nBestBlockTrust = pindexBest->nHeight != 0 ? (pindexBest->nChainTrust - pindexBest->pprev->nChainTrust) : pindexBest->nChainTrust;
+        ? pindexNew->nChainTrust - pindexNew->pprev->nChainTrust
+        : pindexNew->nChainTrust;
+    uint256 nBestBlockTrust = (pindexBest && pindexBest->nHeight != 0 && pindexBest->pprev)
+        ? (pindexBest->nChainTrust - pindexBest->pprev->nChainTrust)
+        : (pindexBest ? pindexBest->nChainTrust : uint256(0));
 
     printf("InvalidChainFound: invalid block=%s  height=%d  trust=%s  blocktrust=%" PRId64 "  date=%s\n",
       pindexNew->GetBlockHash().ToString().substr(0,20).c_str(), pindexNew->nHeight,
@@ -1513,9 +1517,9 @@ void static InvalidChainFound(CBlockIndex* pindexNew)
       DateTimeStrFormat("%x %H:%M:%S", pindexNew->GetBlockTime()).c_str());
     printf("InvalidChainFound:  current best=%s  height=%d  trust=%s  blocktrust=%" PRId64 "  date=%s\n",
       hashBestChain.ToString().substr(0,20).c_str(), nBestHeight,
-      CBigNum(pindexBest->nChainTrust).ToString().c_str(),
+      pindexBest ? CBigNum(pindexBest->nChainTrust).ToString().c_str() : "0",
       nBestBlockTrust.Get64(),
-      DateTimeStrFormat("%x %H:%M:%S", pindexBest->GetBlockTime()).c_str());
+      pindexBest ? DateTimeStrFormat("%x %H:%M:%S", pindexBest->GetBlockTime()).c_str() : "unknown");
 }
 
 
@@ -2536,7 +2540,7 @@ bool CBlock::SetBestChain(CTxDB& txdb, CBlockIndex* pindexNew)
     nTimeBestReceived = GetTime();
     nTransactionsUpdated++;
 
-    uint256 nBestBlockTrust = pindexBest->nHeight != 0 ? (pindexBest->nChainTrust - pindexBest->pprev->nChainTrust) : pindexBest->nChainTrust;
+    uint256 nBestBlockTrust = (pindexBest->nHeight != 0 && pindexBest->pprev) ? (pindexBest->nChainTrust - pindexBest->pprev->nChainTrust) : pindexBest->nChainTrust;
 
     // Log every 5000 blocks during sync, every block once caught up
     if (nBestHeight % 5000 == 0 || !IsInitialBlockDownload())
@@ -3165,7 +3169,7 @@ bool ProcessBlock(CNode* pfrom, CBlock* pblock)
         }
 
         // Ask this guy to fill in what we're missing
-        if (pfrom)
+        if (pfrom && pindexBest)
         {
             pfrom->PushGetBlocks(pindexBest, GetOrphanRoot(pblock2));
             // triangles: getblocks may not obtain the ancestor block rejected