rpc: add missing top block hash to json getinfo call

src/rpc/core_rpc_server.cpp

@@ -1092,7 +1092,14 @@ namespace cryptonote
       return false;
     }
 
-    res.height = m_core.get_current_blockchain_height();
+    crypto::hash top_hash;
+    if (!m_core.get_blockchain_top(res.height, top_hash))
+    {
+      res.status = "Failed";
+      return false;
+    }
+    ++res.height; // turn top block height into blockchain height
+    res.top_block_hash = string_tools::pod_to_hex(top_hash);
     res.target_height = m_core.get_target_blockchain_height();
     res.difficulty = m_core.get_blockchain_storage().get_difficulty_for_next_block();
     res.target = m_core.get_blockchain_storage().get_current_hard_fork_version() < 2 ? DIFFICULTY_TARGET_V1 : DIFFICULTY_TARGET_V2;