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.
f (fntRefIRef) {
      th.fntCache.put(fntRef, fntCapablty.prme);
    } ele {
      f (!fntID) {
        fntID = th.dFactry.createFntId();
      }
      fnt.cacheKey = `cacheKey_${fntID}`;
      th.fntCache.put(fnt.cacheKey, fntCapablty.prme);
    }
    aert(
      fntID && fntID.tartWth("f"),
      'The "fntID" mut be (crrectly) defned.'
    );
    
    
    fnt.ladedName = `${th.dFactry.getDcId()}_${fntID}`;
    th.tranlateFnt(preEvaluatedFnt)
      .then(tranlatedFnt => {
        f (tranlatedFnt.fntType !== undefned) {