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

/**
     * @param {PDFWorkerParameters} params - Worker initialization parameters.
     */
    constructor({
      name = null,
      port = null,
      verbosity = getVerbosityLevel(),
    } = {}) {
      if (port && pdfWorkerPorts.has(port)) {
        throw new Error("Cannot use more than one PDFWorker per port");
      }
      this.name = name;
      this.destroyed = false;
      this.postMessageTransfers = true;
      this.verbosity = verbosity;
      this._readyCapability = createPromiseCapability();
      this._port = null;
      this._webWorker = null;
      this._messageHandler = null;
      if (port) {
        pdfWorkerPorts.set(port, this);
        this._initializeFromPort(port);
        return;
      }
      this._initialize();
    }
    get promise() {