Attach (recommended) or Link to PDF file here:
[issue13075.pdf](https://github.com/mozilla/pdf.js/files/6117265/issue13075.pdf)

Configuration:
- Web browser and its version: Node.js 14.15.5
- Operating system and its version: Mac OS 11.2.1
- PDF.js version: master/2.7.570/2.6.347/1.10.100
- Is a browser extension: false

Steps to reproduce the problem:
1. const fileBuffer = fs.readFileSync('./pdf')
2. PDFJS.getDocument(fileBuffer)
3. fileBuffer.buffer has junk data at the start and at the end. Randomly, pdfjs can not read a buffer, whose buffer.buffer contains random memory junk data in fileBuffer.buffer

What is the expected behavior? pdfjs ignores a buffer.buffer and reads only buffer

What went wrong? (add screenshot)
I've catched that random error and wrote fileBuffer.buffer of the error buffer to a file named issue13075.pdf
I've recreated a buffer that has the wrong buffer.buffer (see line 6). Pdfjs fails to read that buffer (console.log('Fail')).
The Uint8Array of that buffer, pdfjs correctly reads (console.log('OK')).
![image](https://user-images.githubusercontent.com/8398353/110660366-59f1a780-8178-11eb-94c2-29be826c2118.png)


codesandbox:
https://codesandbox.io/s/pdfjs-loading-from-buffer-issue-9h4fd?file=/src/index.js

return this._transport.getPermissions();
  }
  /**
   * @returns {Promise<{ info: Object, metadata: Metadata }>} A promise that is
   *   resolved with an {Object} that has `info` and `metadata` properties.
   *   `info` is an {Object} filled with anything available in the information
   *   dictionary and similarly `metadata` is a {Metadata} object with
   *   information from the metadata section of the PDF.
   */
  getMetadata() {
    return this._transport.getMetadata();
  }
  /**
   * @typedef {Object} MarkInfo
   * Properties correspond to Table 321 of the PDF 32000-1:2008 spec.
   * @property {boolean} Marked
   * @property {boolean} UserProperties
   * @property {boolean} Suspects
   */
  /**
   * @returns {Promise<MarkInfo | null>} A promise that is resolved with
   *   a {MarkInfo} object that contains the MarkInfo flags for the PDF
   *   document, or `null` when no MarkInfo values are present in the PDF file.
   */
  getMarkInfo() {