Merge pull request #1417 from flicker-harmony/pr_crash_fix

Pangaea crash fixes

core/blockchain.go

@@ -822,20 +822,24 @@ func (bc *BlockChain) Rollback(chain []common.Hash) {
 		hash := chain[i]
 
 		currentHeader := bc.hc.CurrentHeader()
-		if currentHeader.Hash() == hash {
+		if currentHeader != nil && currentHeader.Hash() == hash {
 			bc.hc.SetCurrentHeader(bc.GetHeader(currentHeader.ParentHash, currentHeader.Number.Uint64()-1))
 		}
-		if currentFastBlock := bc.CurrentFastBlock(); currentFastBlock.Hash() == hash {
+		if currentFastBlock := bc.CurrentFastBlock(); currentFastBlock != nil && currentFastBlock.Hash() == hash {
 			newFastBlock := bc.GetBlock(currentFastBlock.ParentHash(), currentFastBlock.NumberU64()-1)
+			if newFastBlock != nil {
 				bc.currentFastBlock.Store(newFastBlock)
 				rawdb.WriteHeadFastBlockHash(bc.db, newFastBlock.Hash())
 			}
-		if currentBlock := bc.CurrentBlock(); currentBlock.Hash() == hash {
+		}
+		if currentBlock := bc.CurrentBlock(); currentBlock != nil && currentBlock.Hash() == hash {
 			newBlock := bc.GetBlock(currentBlock.ParentHash(), currentBlock.NumberU64()-1)
+			if newBlock != nil {
 				bc.currentBlock.Store(newBlock)
 				rawdb.WriteHeadBlockHash(bc.db, newBlock.Hash())
 			}
 		}
+	}
 }
 
 // SetReceiptsData computes all the non-consensus fields of the receipts
@@ -1264,13 +1268,15 @@ func (bc *BlockChain) insertChain(chain types.Blocks) (int, []interface{}, []*ty
 			var winner []*types.Block
 
 			parent := bc.GetBlock(block.ParentHash(), block.NumberU64()-1)
-			for !bc.HasState(parent.Root()) {
+			for parent != nil && !bc.HasState(parent.Root()) {
 				winner = append(winner, parent)
 				parent = bc.GetBlock(parent.ParentHash(), parent.NumberU64()-1)
 			}
 			for j := 0; j < len(winner)/2; j++ {
 				winner[j], winner[len(winner)-1-j] = winner[len(winner)-1-j], winner[j]
 			}
+			// Prune in case non-empty winner chain
+			if len(winner) > 0 {
 				// Import all the pruned blocks to make the state available
 				bc.chainmu.Unlock()
 				_, evs, logs, err := bc.insertChain(winner)
@@ -1280,6 +1286,7 @@ func (bc *BlockChain) insertChain(chain types.Blocks) (int, []interface{}, []*ty
 				if err != nil {
 					return i, events, coalescedLogs, err
 				}
+			}
 
 		case err != nil:
 			bc.reportBlock(block, nil, err)