message: [chain]fix chain panic.
diff: @@ -230,7 +230,6 @@ where
  }
  fn get_header(&self, hash: HashValue) -> Result<Option<BlockHeader>> {
  - assert!(self.exist_block(hash));
  let header = if let Some(block) = self.get_block(hash)? {
  Some(block.header().clone())
  } else {
  @@ -335,7 +334,6 @@ where
  Some(hash) => hash,
  None => self.current_header().id(),
  };
  - assert!(self.exist_block(id));
  self.storage.get_block_info(id)
  }
  