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

stringToBytes,
  UnexpectedResponseException,
  UnknownErrorException,
  unreachable,
  warn,
} from "../shared/util.js";
import {
  deprecated,
  DOMCanvasFactory,
  DOMCMapReaderFactory,
  loadScript,
  PageViewport,
  RenderingCancelledException,
  StatTimer,
} from "./display_utils.js";
import { FontFaceObject, FontLoader } from "./font_loader.js";
import { NodeCanvasFactory, NodeCMapReaderFactory } from "./node_utils.js";
import { AnnotationStorage } from "./annotation_storage.js";
import { apiCompatibilityParams } from "./api_compatibility.js";
import { CanvasGraphics } from "./canvas.js";
import { GlobalWorkerOptions } from "./worker_options.js";
import { isNodeJS } from "../shared/is_node.js";
import { MessageHandler } from "../shared/message_handler.js";
import { Metadata } from "./metadata.js";
import { OptionalContentConfig } from "./optional_content_config.js";
import { PDFDataTransportStream } from "./transport_stream.js";
import { WebGLContext } from "./webgl.js";
const DEFAULT_RANGE_CHUNK_SIZE = 65536; 
const RENDERING_CANCELLED_TIMEOUT = 100; 
const DefaultCanvasFactory =