message: nydusctl: fix panic when query nydusd as fscache daemon
  sudo nydusctl --sock api_sock info
  thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', src/bin/nydusctl/commands.rs:369:68
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
  Aborted
diff: @@ -366,8 +366,6 @@ impl CommandDaemon {
  let info = client.get("daemon").await?;
  let i = info.as_object().unwrap();
  - let backend_list = i["backend_collection"].as_object().unwrap();
  -
  if raw {
  println!("{}", info);
  } else {
  @@ -385,11 +383,13 @@ Commit: {git_commit}
  git_commit = version_info["git_commit"],
  );
  - if !backend_list.is_empty() {
  + if let Some(b) = i.get("backend_collection") {
  + if let Some(fs_backends) = b.as_object() {
  + if !fs_backends.is_empty() {
  println!("Backend list:")
  }
  - for (mount_point, backend_obj) in backend_list {
  + for (mount_point, backend_obj) in fs_backends {
  let backend: FsBackendDesc =
  serde_json::from_value(backend_obj.clone()).unwrap();
  println!(" {}", mount_point);
  @@ -400,7 +400,8 @@ Commit: {git_commit}
  FsBackendType::PassthroughFs => {}
  FsBackendType::Rafs => {
  let fs: RafsConfig =
  - serde_json::from_value(backend.config.unwrap().clone()).unwrap();
  + serde_json::from_value(backend.config.unwrap().clone())
  + .unwrap();
  print!(
  r#" Mode: {meta_mode}
  Prefetch: {enabled}
  @@ -415,6 +416,8 @@ Commit: {git_commit}
  }
  }
  }
  + }
  + }
  Ok(())
  }
  