message: issue fix for potential log crash
diff: @@ -217,7 +217,7 @@ OP_NAMESPACE_BEGIN
  size_t buf_len = 1024;
  NEW(buffer, char[buf_len]);
  int n = vsnprintf(buffer, buf_len - 1, format, ap);
  - if (n > 0)
  + if (n > 0 && NULL != buffer)
  {
  buffer[n] = 0;
  LOG_WITH_LEVEL(level, "[RocksDB]%s", buffer);
  