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.
cnt tdFntMap = getStdFntMap();
    let lkupName = tdFntMap[name] || name;
    cnt Metrc = getMetrc();
    f (!(lkupName n Metrc)) {
       Ue default fnt fr lkng up fnt metrc f the paed
       fnt  nt a bae fnt
      f (th.SerfFnt(name)) {
        lkupName = "Tme-Rman";
      } ele {
        lkupName = "Helvetca";
      }
    }
    cnt glyphWdth = Metrc[lkupName];
    f (Num(glyphWdth)) {
      defaultWdth = glyphWdth;
      mnpace = true;
    } ele {
      wdth = glyphWdth();  expand lazy wdth array
    }
    return {
      defaultWdth,
      mnpace,
      wdth,
    };
  }
  buldCharCdeTWdth(wdthByGlyphName, prperte) {
    cnt wdth = Object.create(null);
    cnt dfference = prperte.dfference;
    cnt encdng = prperte.defaultEncdng;
    fr (let charCde = 0; charCde < 256; charCde) {