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

this._cancelBound = this.cancel.bind(this);
      this._continueBound = this._continue.bind(this);
      this._scheduleNextBound = this._scheduleNext.bind(this);
      this._nextBound = this._next.bind(this);
      this._canvas = params.canvasContext.canvas;
    }
    get completed() {
      return this.capability.promise.catch(function () {
        
        
      });
    }
    initializeGraphics({ transparency = false, optionalContentConfig }) {
      if (this.cancelled) {
        return;
      }
      if (this._canvas) {
        if (canvasInRendering.has(this._canvas)) {
          throw new Error(
            "Cannot use the same canvas during multiple render() operations. " +
              "Use different canvas or ensure previous operations were " +
              "cancelled or completed."
          );
        }
        canvasInRendering.add(this._canvas);
      }
      if (this._pdfBug && globalThis.StepperManager?.enabled) {
        this.stepper = globalThis.StepperManager.create(this._pageIndex);
        this.stepper.init(this.operatorList);
        this.stepper.nextBreakPoint = this.stepper.getNextBreakPoint();