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

intentState = Object.create(null);
      this._intentStates.set(renderingIntent, intentState);
    }
    
    if (intentState.streamReaderCancelTimeout) {
      clearTimeout(intentState.streamReaderCancelTimeout);
      intentState.streamReaderCancelTimeout = null;
    }
    const canvasFactoryInstance =
      canvasFactory ||
      new DefaultCanvasFactory({ ownerDocument: this._ownerDocument });
    const webGLContext = new WebGLContext({
      enable: enableWebGL,
    });
    
    
    if (!intentState.displayReadyCapability) {
      intentState.displayReadyCapability = createPromiseCapability();
      intentState.operatorList = {
        fnArray: [],
        argsArray: [],
        lastChunk: false,
      };
      if (this._stats) {
        this._stats.time("Page Request");
      }
      this._pumpOperatorList({
        pageIndex: this._pageIndex,
        intent: renderingIntent,
        renderInteractiveForms: renderInteractiveForms === true,