我正在尝试从Firebase Cloud函数中的Firebase Storage下载文件，其中包含以下类型脚本代码：

exports.getProfileImage = functions.https.onRequest(async (req, resp) => {
  const authHeader = req.headers.authorization;
  if (!authHeader || !authHeader.startsWith("Bearer ")) {
    resp.status(401).send("Unauthorized");
    return;
  }
  let detail = "start";
  let decodedToken: DecodedIdToken;
  try {
    const idToken = authHeader.split("Bearer ")[1];
    try {
      decodedToken = await admin.auth().verifyIdToken(idToken);
    } catch (e) {
      resp.status(401).send("Unauthorized");
      return;
    }
    const match = RegExp("^\\/(\\w+)$").exec(req.path);
    const uid = match && match[1];
    if (!uid) {
      resp.status(400).send(`Invalid profile image request: ${req.path}`);
      return;
    }
    const filePath = `user/${uid}/profileImage`;
    detail = `locating file ${filePath}`;
    const ref = admin.storage().bucket().file(filePath);
    detail = "Checking file exists";
    if (!await ref.exists()) {
      resp.status(404).send(`Requested profile image not found: ${req.path}`);
      return;
    }
    detail = `Downloading profile image for ${decodedToken.email} ` +
      `from ${ref.cloudStorageURI.href}`;
    const [fileContent] = await ref.download();
    resp.type("jpeg");
    detail = "Sending result";
    resp.send(fileContent);
    return;
  } catch (e) {
    if (e instanceof Error) {
      resp.status(500).send(`Error while retrieving image: ${e.message}.` +
        `Occurred during ${detail}`);
    } else {
      resp.status(500).send("Unknown error retrieving image");
    }
  }
});

我不明白为什么exists显然会返回true，但下载会失败，并显示消息“没有这样的对象”。在“download”行上抛出异常，导致类似“Error while retrieving image：没有这样的物体[.]”
我用createReadStream替换下载代码时也会出现类似的错误：

detail = `Downloading profile image for ${decodedToken.email} ` +
  `from ${ref.cloudStorageURI.href}`;
const fileReader = ref.createReadStream();
detail = "Setting type to jpeg";
resp.type("jpeg");
detail = "Piping file content to response";
fileReader.on("error", (err) => resp.status(500).send(err.message))
  .pipe(resp);
detail = "Sending result";
return;