Attach (recommended) or Link to PDF file here:
https://bitcoin.org/bitcoin.pdf

Configuration:
- Web browser and its version: all
- Operating system and its version: all
- PDF.js version: tested with 2.9.11, but most likely all versions
- Is a browser extension: no

Steps to reproduce the problem:
1. Type "a purely" (single space between "a" and "purely") - doesn't find anything
2. Type "a  purely" (two spaces between "a" and "purely") - finds the phrase

Sometimes even 3 spaces are necessary.

What is the expected behavior? (add screenshot)
![Screenshot from 2021-04-08 13-00-03](https://user-images.githubusercontent.com/6362989/114008903-57639a00-986b-11eb-903a-92bbebbd922b.png)

What went wrong? (add screenshot)
![Screenshot from 2021-04-08 13-01-53](https://user-images.githubusercontent.com/6362989/114008810-44e96080-986b-11eb-8232-f58a62ed7899.png)

This affects many PDFs because justify alignment is common enough.
expect(pageIndex).toEqual(1);
    });
    it("gets invalid page index", async function () {
      const ref = { num: 3, gen: 0 }; 
      try {
        await pdfDocument.getPageIndex(ref);
        
        expect(false).toEqual(true);
      } catch (reason) {
        expect(reason instanceof Error).toEqual(true);
      }
    });
    it("gets destinations, from /Dests dictionary", async function () {
      const destinations = await pdfDocument.getDestinations();
      expect(destinations).toEqual({
        chapter1: [{ gen: 0, num: 17 }, { name: "XYZ" }, 0, 841.89, null],
      });
    });
    it("gets a destination, from /Dests dictionary", async function () {
      const destination = await pdfDocument.getDestination("chapter1");
      expect(destination).toEqual([
        { gen: 0, num: 17 },
        { name: "XYZ" },
        0,
        841.89,
        null,
      ]);
    });
    it("gets a non-existent destination, from /Dests dictionary", async function () {
      const destination = await pdfDocument.getDestination(