Attach (recommended) or Link to PDF file here:
See pdf in https://github.com/mozilla/pdf.js/issues/3109

Configuration:
- Web browser and its version: Firefox nightly
- Operating system and its version: Windows 10
- PDF.js version: builtin viewer

Steps to reproduce the problem:
1. Look at outlines

What is the expected behavior? (add screenshot)
![image](https://user-images.githubusercontent.com/5641725/141514798-0e656865-1cbf-4fb8-a89b-530d36da23c9.png)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/5641725/141514740-c95e0237-8bf4-4129-a4a5-cb2ea5a3f4df.png)

const length = arr.length;
  
  if (length === 1 && arr[0] instanceof Uint8Array) {
    return arr[0];
  }
  let resultLength = 0;
  for (let i = 0; i < length; i++) {
    resultLength += arrayByteLength(arr[i]);
  }
  let pos = 0;
  const data = new Uint8Array(resultLength);
  for (let i = 0; i < length; i++) {
    let item = arr[i];
    if (!(item instanceof Uint8Array)) {
      if (typeof item === "string") {
        item = stringToBytes(item);
      } else {
        item = new Uint8Array(item);
      }
    }
    const itemLength = item.byteLength;
    data.set(item, pos);
    pos += itemLength;
  }
  return data;
}
function string32(value) {