From a6df99fc9c34e56e6ac10faf049e915cb8602579 Mon Sep 17 00:00:00 2001
From: jl777 <jameslee777@yahoo.com>
Date: Thu, 28 Sep 2017 22:08:32 +0300
Subject: [PATCH] Getchaintips error checks

---
 src/rpcblockchain.cpp | 58 +++++++++++++++++++++++--------------------
 1 file changed, 31 insertions(+), 27 deletions(-)

diff --git a/src/rpcblockchain.cpp b/src/rpcblockchain.cpp
index e4574860c..d4f65f940 100644
--- a/src/rpcblockchain.cpp
+++ b/src/rpcblockchain.cpp
@@ -1055,7 +1055,9 @@ UniValue getchaintips(const UniValue& params, bool fHelp)
         setTips.insert(item.second);
     BOOST_FOREACH(const PAIRTYPE(const uint256, CBlockIndex*)& item, mapBlockIndex)
     {
-        const CBlockIndex* pprev = item.second->pprev;
+        const CBlockIndex* pprev=0;
+        if ( item.second != 0 )
+            pprev = item.second->pprev;
         if (pprev)
             setTips.erase(pprev);
     }
@@ -1064,38 +1066,40 @@ UniValue getchaintips(const UniValue& params, bool fHelp)
     setTips.insert(chainActive.Tip());
 
     /* Construct the output array.  */
-    UniValue res(UniValue::VARR);
+    UniValue res(UniValue::VARR); CBlockIndex *forked;
     BOOST_FOREACH(const CBlockIndex* block, setTips)
     {
         UniValue obj(UniValue::VOBJ);
         obj.push_back(Pair("height", block->nHeight));
         obj.push_back(Pair("hash", block->phashBlock->GetHex()));
-
-        const int branchLen = block->nHeight - chainActive.FindFork(block)->nHeight;
-        obj.push_back(Pair("branchlen", branchLen));
-
-        string status;
-        if (chainActive.Contains(block)) {
-            // This block is part of the currently active chain.
-            status = "active";
-        } else if (block->nStatus & BLOCK_FAILED_MASK) {
-            // This block or one of its ancestors is invalid.
-            status = "invalid";
-        } else if (block->nChainTx == 0) {
-            // This block cannot be connected because full block data for it or one of its parents is missing.
-            status = "headers-only";
-        } else if (block->IsValid(BLOCK_VALID_SCRIPTS)) {
-            // This block is fully validated, but no longer part of the active chain. It was probably the active block once, but was reorganized.
-            status = "valid-fork";
-        } else if (block->IsValid(BLOCK_VALID_TREE)) {
-            // The headers for this block are valid, but it has not been validated. It was probably never part of the most-work chain.
-            status = "valid-headers";
-        } else {
-            // No clue.
-            status = "unknown";
+        forked = chainActive.FindFork(block);
+        if ( forked != 0 )
+        {
+            const int branchLen = block->nHeight - forked->nHeight;
+            obj.push_back(Pair("branchlen", branchLen));
+            
+            string status;
+            if (chainActive.Contains(block)) {
+                // This block is part of the currently active chain.
+                status = "active";
+            } else if (block->nStatus & BLOCK_FAILED_MASK) {
+                // This block or one of its ancestors is invalid.
+                status = "invalid";
+            } else if (block->nChainTx == 0) {
+                // This block cannot be connected because full block data for it or one of its parents is missing.
+                status = "headers-only";
+            } else if (block->IsValid(BLOCK_VALID_SCRIPTS)) {
+                // This block is fully validated, but no longer part of the active chain. It was probably the active block once, but was reorganized.
+                status = "valid-fork";
+            } else if (block->IsValid(BLOCK_VALID_TREE)) {
+                // The headers for this block are valid, but it has not been validated. It was probably never part of the most-work chain.
+                status = "valid-headers";
+            } else {
+                // No clue.
+                status = "unknown";
+            }
+            obj.push_back(Pair("status", status));
         }
-        obj.push_back(Pair("status", status));
-
         res.push_back(obj);
     }