Merge branch 'develop' into qt5.4

core/chain_manager.go

@@ -251,7 +251,13 @@ func (self *ChainManager) GetBlockHashesFromHash(hash []byte, max uint64) (chain
 
 	// XXX Could be optimised by using a different database which only holds hashes (i.e., linked list)
 	for i := uint64(0); i < max; i++ {
-		block = self.GetBlock(block.Header().ParentHash)
+		parentHash := block.Header().ParentHash
+		block = self.GetBlock(parentHash)
+		if block == nil {
+			chainlogger.Infof("GetBlockHashesFromHash Parent UNKNOWN %x\n", parentHash)
+			break
+		}
+
 		chain = append(chain, block.Hash())
 		if block.Header().Number.Cmp(ethutil.Big0) <= 0 {
 			break