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

if (worker.destroyed) {
    return Promise.reject(new Error("Worker was destroyed"));
  }
  if (pdfDataRangeTransport) {
    source.length = pdfDataRangeTransport.length;
    source.initialData = pdfDataRangeTransport.initialData;
    source.progressiveDone = pdfDataRangeTransport.progressiveDone;
    source.contentDispositionFilename =
      pdfDataRangeTransport.contentDispositionFilename;
  }
  return worker.messageHandler
    .sendWithPromise("GetDocRequest", {
      docId,
      apiVersion:
        typeof PDFJSDev !== "undefined" && !PDFJSDev.test("TESTING")
          ? PDFJSDev.eval("BUNDLE_VERSION")
          : null,
      
      source: {
        data: source.data,
        url: source.url,
        password: source.password,
        disableAutoFetch: source.disableAutoFetch,
        rangeChunkSize: source.rangeChunkSize,
        length: source.length,
      },
      maxImageSize: source.maxImageSize,
      disableFontFace: source.disableFontFace,
      postMessageTransfers: worker.postMessageTransfers,
      docBaseUrl: source.docBaseUrl,